01 - The shift
The road from Seed to Series A has lengthened
Across venture, the time between rounds has been stretching. Industry data puts the gap from Seed to Series A at roughly 2.1 years today, up from about 1.5 years five years ago. Companies are staying longer between raises, and raising more to get there: extension rounds accounted for around 29% of Seed deals in 2025, a sign that a single Seed round increasingly does not carry a company all the way to a Series A.
Deep technology feels this most acutely. These companies are capital-intensive and physical; the path from a working result to commercial proof runs through manufacturing, qualification, regulation and real-world deployment, none of which move at software speed. The practical effect is a window of roughly 22 to 30 months that deep tech companies are now spending between their Seed round and Series A.
The time deep tech companies now spend between their Seed round and a Series A.
Seed to Series A across venture, up from about 1.5 years five years ago.
Share of 2025 Seed deals that were extension rounds, companies raising again to fund a longer path.
02 - What the window is for
From scientific risk to execution risk
What makes this stage distinct is not just its length but the kind of risk that dominates it. A company entering the window has, in most cases, already shown that its core science works, the validation that justified the Seed round. The remaining open questions are different in nature. Can the technology hold up outside the lab? Can it integrate into a customer's existing systems and workflows? Is there commercial evidence, pilots, early contracts, adoption, that the market will pay for? Can it be made reliably at scale and, where relevant, can it be qualified or certified?
These are execution questions, and they are precisely the ones that a Seed Window can underwrite. The work of the window is to fund the transition between demonstrated science (i.e., technical validation) into the operational evidence (i.e., real-world execution) that prices the next round.
Entering the window, the science is largely proven.
To leave it, execution is what has to be proven.
This is also what makes the phase genuinely hard to finance. It is no longer pure science, fundable on promise, and not yet a growth company, fundable on metrics. It sits in between, too real to be treated as a research project, too early to be read through clean operating numbers.
03 - Why the gap persists
Why a gap this visible stays open
This gap is neither hidden nor new. Several structural features explain why it has stayed open anyway.
It falls between mandates. Funds are built for a stage, and this one sits between two. Seed funds are sized, paced and priced for earlier entry; Series A funds underwrite against operating metrics that a company in the window does not yet have. The phase is less neglected than structurally awkward, it does not fit cleanly on either side of a line that was drawn before the gap widened.
The diligence is a different discipline. Assessing a company here means judging whether execution is holding, whether reliability, integration, qualification and customer evidence are improving, rather than extrapolating from metrics. That is a technical and operational assessment, requiring a specialised combination of skill sets to evaluate.
Extension capital is the path of least resistance. Existing investors can fund the gap on information they already hold, without fresh diligence or a repricing conversation. That is much of why extension rounds have grown to around 29% of Seed deals: the most available capital at this stage is defensive support from insiders rather than capital dedicated to the phase.
And pricing is genuinely hard. A company in the window is materially de-risked since its Seed round but has no obvious comparable set to price against. Where a valuation is difficult to establish, both sides often prefer to defer it, which extends the window further and reinforces the pattern.
04 - Crossing it
What getting through the window takes
If the window is a stage, it has a job and work attached to it. The companies that cross it well tend to treat the period as a sequence of specific proof points rather than a general push for traction. What a later investor underwrites is narrower than it looks: evidence that the technology performs outside controlled conditions, a pilot that a customer has actually qualified rather than just performed, and some signal of repeatability, a second site, a second customer, a renewed contract.
Sequencing matters more here than in software, because several of these steps have lead times that capital cannot compress. Certification, regulatory review, industrial qualification and customer procurement move at institutional speed. A company that begins them late can find its runway determined by a queue rather than by its own progress, which is one reason the window stretches well beyond the average for some businesses.
05 - Why it becomes a category
The Pre-seed precedent
There is precedent for a funding gap hardening into a recognised stage. In the early 2010s, Seed itself drifted later. A gap opened ahead of it, Pre-seed professionalised to fill that gap, and by around 2017 Pre-seed was an established venture category with dedicated managers. The pattern was simple: rounds moving later create gaps, and persistent gaps create categories.
The same dynamic now appears to be playing out one stage up, between Seed and Series A. The gap has widened, it has stayed open, and validated deep tech companies increasingly need dedicated capital to cross it.
06 - Conclusion
A stage forming in plain sight
The gap between Seed and Series A has widened into a distinct 22-30 month window, a phase with its own dominant risk, its own milestones, and its own capital needs. It is where a deep tech company stops proving that its science can exist and starts proving that it can execute: reliably, commercially, and at a standard a Series A investor can underwrite.
Whether or not the stage settles on a single name, treating it as a real phase, rather than reading Seed as a single moment followed by a wait, is the more precise way to understand how deep technology is now financed and built.
Rounds moving later create gaps. Persistent gaps create categories. The gap between Seed and Series A has been open long enough to start becoming one. This presents a new opportunity and entry point for specialised investors.