Free tools Windows power users keep installed
One-click scans. No signup required.
Theiler stages (TS) are the standard way to describe mouse embryo development by visible anatomy. The embryonic period proper is divided into 26 morphology-based stages, TS01–TS26. Approximate days post coitum (dpc, often written E-days) help with orientation, but age is not a substitute for staging: embryos of the same gestational age can be at different stages, and different mouse strains develop at different rates. The timeline below uses the reference mapping for C57BL/6 × CBA F1 embryos and should be treated as a guide rather than a set of universal deadlines.
The atlas convention used here calls the morning after a vaginal plug is found 0.5 dpc. In that system, TS01 is approximately 0.5 dpc and TS26 approximately 18 dpc. Implantation and egg-cylinder formation occur around TS05–TS08, gastrulation and primitive-streak changes around TS09–TS10, the first somites at TS12, and posterior neuropore formation with a visible forelimb-bud condensation at TS15.
As an Amazon Associate I earn from qualifying purchases.
What a Theiler stage tells you
A Theiler stage is a morphological classification. It identifies an embryo by landmarks that can be seen in the whole specimen or in an anatomical model, such as implantation status, egg-cylinder shape, primitive-streak organization, neural folds, somites, turning, limb buds, digits, eyes and tail development. The system is therefore more informative than an age label when embryos have developed at slightly different rates.
The e-Mouse Atlas Project (EMAP) states: “Embryos of the same gestational age may differ in their stage of development.” It also notes that “Different mouse strains develop at different rates and, in some cases show differences in the relative rates of development of different organs.” Those qualifications apply to every dpc equivalent in this guide.
#1 Best Overall
- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
- Aluminum Alloy Housing: Built with a sturdy aluminum alloy shell that aids in heat dissipation and protects against daily wear and scratches. Designed to maintain a stable and secure connection.
- Compact & Travel-Friendly: The ultra-compact design allows the adapter to stay plugged into your device without blocking adjacent ports or adding bulk, reducing wear and tear on your original USB ports.
- 12-Month Warranty: Backed by a 12-month manufacturer warranty for peace of mind. Designed to meet strict quality control standards for reliable everyday performance.
EMAP’s electronic atlas is based on Theiler and Kaufman, adding staged anatomical models and a structured anatomical vocabulary. The 26-stage count refers to the embryonic period proper; it does not include postnatal growth. See the EMAP overview and the Theiler stage definitions for the formal criteria.
How dpc or E-day dating works
Researchers usually record the day a vaginal plug is found and use the following morning as 0.5 dpc (E0.5). This convention gives a practical clock, not an exact developmental timestamp. Mating time, plug-detection accuracy, strain, litter conditions and individual variation all affect how closely age matches anatomy.
Use dpc to describe the breeding context and TS to describe what is actually visible. A statement such as “TS12, collected at 8 dpc from a C57BL/6 × CBA F1 pregnancy” is more reproducible than “an 8-day embryo,” because it records both morphology and the approximate age context.
Quick wins for a faster PC:
Scan for outdated or missing drivers - takes under a minuteDriver Scan →Repair Windows errors before they cause bigger problemsFix Now →Mouse embryo timeline: TS01 through TS26
The table gives the principal reference groupings. The dpc values are approximate ranges from EMAP material for C57BL/6 × CBA F1 embryos, not universal cutoffs. “Typical somite” counts are useful only in the early stages and become unreliable as a general staging method after TS12.
| Theiler stages | Approximate dpc | Key developmental landmarks | How to use the estimate |
|---|---|---|---|
| TS01 | 0.5 | One-cell egg | Earliest reference point; confirm with cleavage timing and specimen context. |
| TS02 | Approximately 1–2 | Early cleavage before the morula range | Age is especially approximate; cell number can supplement morphology. |
| TS03–TS04 | Approximately 2–3 | Morula through blastocyst | Use embryo architecture and cell number rather than dpc alone. |
| TS05–TS08 | Approximately 4–6 | Zona-free blastocyst, attachment, implantation and egg-cylinder differentiation | Implantation status is a stronger landmark than an assumed calendar day. |
| TS09–TS10 | Approximately 6.5–7 | Early-streak through late-streak stages; the allantoic bud begins at TS10 late-streak early-bud | Primitive-streak and allantoic morphology identify the transition. |
| TS11–TS12 | Approximately 7.5–8 | Neural-plate development through the first somites; TS12 is unturned with 1–7 somite pairs | At TS12, head folds, neural closure and rapid heart-rudiment development are important landmarks. |
| TS13–TS15 | Approximately 8.5–9.5 | Head-fold and turning progression; at TS15 the posterior neuropore and forelimb-bud condensation are apparent | Use overall shape and neural/limb landmarks together. |
| TS16–TS20 | Approximately 10–12 | Organogenesis and continuing external morphological change | Eye, limb, tail and other organ landmarks become more useful than somite counts. |
| TS21–TS26 | Approximately 13–18 | Later fetal development through the end of the embryonic period | Digit separation and maturation of external structures help distinguish later stages. |
For the formal stage-by-stage descriptions and the atlas’ stated ranges, consult EMAP’s staging criteria and stage-definition table.
TS01–TS04: cleavage, morula and blastocyst
TS01: the one-cell egg
TS01 is the one-cell stage and is mapped to approximately 0.5 dpc in the C57BL/6 × CBA F1 reference series. It marks the beginning of the 26-stage embryonic sequence used by the atlas. At this point, a calendar estimate is generally more useful for describing the collection protocol than for predicting a precise morphological appearance.
TS02: early cleavage
Cleavage divisions produce progressively more cells without the embryo immediately becoming larger as a whole. EMAP’s broad reference mapping places this transition between the one-cell stage and the morula range. Because cleavage timing varies, report the observed cell number when it is clear and retain the dpc value as context.
Recommended Free Tools
Rank #2
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
- Quick Data Transfers: Accelerate your productivity with rapid data transfers using a high-speed 5Gbps USB 3.0 port and two 480Mbps USB 2.0 ports.
- 4K HDMI Display: Enhance your visual experience with a hub capable of delivering 4K resolution at 30Hz in both mirror and extend modes. Please note that this hub is compatible with MacBook (macOS 12 and newer), Windows 10 and 11, ChromeOS, and laptops equipped with DP Alt Mode and Power Delivery. Note: This device is not compatible with Linux.
- What You Get: Anker USB-C Hub (5-in-1, 4K HDMI), welcome guide, 18-month warranty, and our friendly customer service.
TS03–TS04: morula to blastocyst
TS03–TS04 correspond approximately to 2–3 dpc in the reference series and cover the morula-to-blastocyst transition. The blastocyst is the stage at which the early embryo has organized into a more complex structure before leaving the zona pellucida and interacting with the uterus. A precise TS assignment should follow the atlas morphology rather than a presumed day alone.
TS05–TS08: zona loss, attachment and implantation
TS05–TS06: the preimplantation-to-implantation transition
Across TS05–TS08, approximately 4–6 dpc in the reference mapping, the embryo progresses from a zona-free blastocyst to attachment and implantation. The changing relationship between the embryo and uterine tissue is a central staging landmark. The same nominal dpc can contain embryos that have not reached exactly the same implantation state.
TS07–TS08: implantation and egg-cylinder differentiation
TS07–TS08 are associated with implantation and the transition to an egg-cylinder configuration. This is a major change in organization: the embryo is no longer simply a free blastocyst, and the geometry of the egg cylinder provides a more useful developmental description than a day number. The approximate 4–6 dpc range is strain-contextual, not a deadline that every pregnancy follows.
TS09–TS10: gastrulation and the primitive streak
TS09: early-streak development
TS09 falls in the early-streak portion of the approximately 6.5–7 dpc reference interval. Gastrulation reorganizes the embryo and establishes the primitive-streak axis. When staging, record the extent and position of the streak and the overall egg-cylinder morphology, rather than inferring the stage from age alone.
The Tool Desk
Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →TS10: late streak and the first allantoic bud
TS10 covers late-streak subdivisions and the early-bud transition. In the late-streak early-bud subdivision, the allantoic bud first appears. That feature is especially useful because it marks a visible change within the gastrulation-to-bud sequence.
EMAP provides the dedicated TS10 definition. Use its images and criteria when deciding whether a specimen is still in a late-streak description or has entered the early-bud subdivision.
TS11–TS12: neural plate, somites and the early heart
TS11: neural-plate development
TS11 bridges the streak/early-bud sequence and the first-somite stage. Neural-plate formation and shaping become prominent landmarks. At these young stages, somite counts can supplement surface observations, but they should be recorded alongside the whole-embryo morphology.
Rank #3
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
- Flawless 4K@60Hz Video with HDMI: Delivers exceptional clarity and smoothness with its 4K@60Hz HDMI port, making it ideal for high-definition presentations and entertainment. (Note: Only the HDMI port supports video projection; the USB-C port is for data transfer only.)
- Double Up on Efficiency: The two USB-A 3.0 ports and a USB-C port support a fast 5Gbps data rate, significantly boosting your transfer speeds and improving productivity.
- Fast and Reliable 85W Charging: Offers high-capacity, speedy charging for laptops up to 85W, so you spend less time tethered to an outlet and more time being productive.
- What You Get: Anker USB-C Hub (7-in-1), welcome guide, 18-month warranty, and our friendly customer service.
TS12: the first-somite stage
TS12 is mapped to approximately 8 dpc, with an atlas range of about 7.5–8.75 dpc. The embryo remains unturned and has 1–7 somite pairs. Head folds and neural closure are developing, while the heart rudiment changes rapidly.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
The combination matters: a specimen with a few somite pairs should not be assigned TS12 automatically if its head-fold or overall shape does not match. Conversely, a dpc value near 8 does not guarantee TS12. The dedicated TS12 criteria provide the formal visual reference.
TS13–TS15: turning, neuropore closure and the first limb bud
TS13–TS14: head-fold and turning progression
TS13–TS14, approximately 8.5–9 dpc in the reference series, mark continuing head-fold development and the transition toward turning. The embryo’s three-dimensional shape changes quickly, so orientation and overall curvature should be documented when comparing specimens.
TS15: posterior neuropore and forelimb-bud condensation
TS15 is listed at approximately 9.5 dpc, with a reference range of about 9–10.25 dpc. The posterior neuropore forms, and condensation in the forelimb bud is apparent. These landmarks distinguish TS15 from earlier head-fold stages and make it more informative than a simple “day 9” label.
See EMAP’s TS15 definition for the stage-specific criteria. When comparing two embryos near this transition, note whether each has the posterior neuropore feature and whether forelimb-bud condensation is visible, then report the dpc and strain.
Do these 3 things before closing this tab:
1Scan for outdated or missing drivers - takes under a minute2Repair Windows errors before they cause bigger problems3Fix the driver behind crashes, sound loss and screen glitchesTS16–TS20: organogenesis and external shape
TS16–TS20 span approximately 10–12 dpc in the reference grouping. Organ systems continue to form and mature while external morphology changes rapidly. This interval is best staged by several landmarks together rather than by one measurement.
- Neural and body shape: assess continued closure and the degree of turning.
- Limb development: follow the changing forelimb and hindlimb outlines and the progression toward recognizable distal structures.
- Eye and tail development: these become useful external indicators in older embryos.
- Overall anatomy: record the combination of landmarks, because organ systems do not all advance at identical rates.
After TS12, somite number should not be used as a reliable global indicator of stage. A specimen can have a somite count that sounds plausible for a particular day while its limb, eye or tail development places it elsewhere in the Theiler sequence.
Rank #4
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
- Upgraded Exquisite Craftsmanship: With an aluminum alloy housing and metal connector, the usbc to usb adapter is extremely durable and sturdy. Rigorously tested to withstand more than 10,000 times of plugging and unplugging, ensuring long-lasting performance
- Broad Compatible: The usb c to usb adapter widely supports all USB C/ USB A devices like laptops, tablets, cellphones, car chargers, and phone chargers. Such as compatible with MacBook Pro/Air 2023/2022, Thunderbolt 4/3 Devices,Apple MagSafe Watch 9/8/7/SE/Ultra, iPad Pro 2022/2021, Samsung Galaxy S23/S20/S10, and iPhone 17/16/15 Pro. Plug and play
- Please Note: To reach 10Gbps speed, keep the cable under 3.3 ft. For USB A Male to USB C adapters, try flipping the USB C connector. USB C Male to USB A adapters support bidirectional 10Gbps transfer within 3.3 ft
TS21–TS26: later fetal morphology and the end of the embryonic period
TS21–TS26 correspond approximately to 13–18 dpc in the C57BL/6 × CBA F1 reference series. These stages cover later fetal development through the end of the embryonic period used by the atlas. External features become increasingly descriptive: limb and digit morphology, eye development, tail shape and other visible structures help separate neighboring stages.
Digit separation and continued maturation are useful late-stage landmarks, but the exact transition from one stage to the next must follow the atlas criteria. Do not extend the “26 stages” label into postnatal development; TS26 is the final stage in this embryonic-period classification, not a claim that development ends at birth.
How to stage a mouse embryo in practice
- Record the context. Write down strain or cross, plug date, collection time, the dpc convention, litter and specimen identifiers.
- Start with whole-embryo morphology. Note implantation status, egg-cylinder shape, primitive streak, neural folds, turning and the general body outline.
- Use age only as an orientation. Compare the observed anatomy with the approximate dpc range for candidate Theiler stages.
- Add age-appropriate counts. In younger embryos, record cell number or somite pairs when they are clearly visible. Treat these as supporting observations, not as a replacement for morphology.
- For older embryos, switch landmarks. Assess eye, limb, tail and digit development. Do not use somite number alone after TS12.
- Assign the closest stage and state uncertainty. If features fall between criteria, report a stage range or “approximately TS” and explain which landmark was decisive.
- Check the formal definition. Compare the specimen with EMAP’s staging-criteria page and the relevant stage-specific entry before finalizing a record.
How to compare two embryos without overclaiming
Use the same four axes for every comparison:
- Morphological landmark: state exactly what is present, such as an allantoic bud, a somite pair, a posterior neuropore or forelimb-bud condensation.
- Theiler stage: give TS01–TS26, or a narrow range if the specimen is transitional.
- Approximate age and strain: include dpc and the breeding background, because the atlas mapping is strain-contextual.
- Confidence and limits: explain whether the assignment rests on several concordant features or on a partially visible landmark.
For example, “Embryo A is approximately TS15, collected at 9.5 dpc, with a visible posterior neuropore and forelimb-bud condensation; Embryo B is earlier because those features are not yet apparent” is a stronger comparison than “A is day 9.5 and B is day 9.” The first statement separates observed anatomy from the approximate calendar context.
Common staging mistakes and how to correct them
Treating dpc as an exact stage
Problem: assigning every embryo from a plug-positive morning to one fixed TS.
Correction: use dpc as a range and verify morphology. EMAP explicitly warns that embryos of the same gestational age may differ in stage.
Assuming every strain follows the reference table
Problem: applying the C57BL/6 × CBA F1 mapping to another strain or cross without qualification.
Correction: identify the strain and call the table an approximate reference. Strain-specific developmental rates can shift the relationship between age and visible anatomy.
Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
- Transfer Files in Seconds: Move files to and from your laptop at speeds of up to 5 Gbps via the USB-C and USB-A data ports. Note: The USB C 5Gbps Data port does not support video output.
- HD Display: Connect to the HDMI port to stream or mirror content to an external monitor in resolutions of up to 4K@30Hz. Note: The USB-C ports do not support video output.
- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
Using somites as a universal clock
Problem: inferring the entire embryo’s stage from a somite count after TS12.
Correction: combine early somite observations with head and neural morphology, and use eye, limb and tail development for older embryos.
Ignoring organ-specific differences
Problem: assuming all organs mature at the same relative rate.
PC Slower Than It Used to Be?
A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11Crashes, No Sound, or Screen Glitches?
Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteCorrection: document several systems. EMAP notes that strains can differ not only in overall rate but also in the relative rates of development of different organs.
Confusing embryonic stages with postnatal ages
Problem: describing TS26 as the end of all mouse development.
Correction: state that TS01–TS26 cover the embryonic period proper. Postnatal growth requires a different age and developmental framework.
Reference resources for deeper work
The free EMAP electronic atlas supplies stage criteria, anatomical models and terminology. For a printed anatomical reference, Springer lists Karl Theiler’s The House Mouse: Atlas of Embryonic Development, softcover ISBN 978-3-642-88420-7, on its publisher page. Check the publisher’s current edition and availability details when obtaining the book.
The most defensible record combines the atlas stage, visible landmarks, approximate dpc, strain and any uncertainty. That format lets another researcher understand both what was observed and how much confidence to place in the age equivalent.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
