Conception Says It Has Made Early Human Egg Cells From Stem Cells

Why it matters

Conception's claim moves IVG closer to a testable fertility platform, but the startup still has to prove maturation, safety, and regulatory viability.

Matt Krisiloff (@mattkrisiloff) said Conception has generated early human egg cells from stem cells, the clearest public milestone yet for the Berkeley fertility startup's attempt to make egg supply a manufactured biological process rather than a fixed constraint.

Krisiloff, Conception's co-founder and CEO, posted the update in a thread on X on June 30, writing that the company had converted blood cells into stem cells and then guided those cells into what Conception describes as miniature human ovaries containing early eggs. In a company blog post, Conception calls the cells "primary oocytes," a very early stage of egg development.

The distinction matters. Conception is not claiming that it has made mature, fertilizable human eggs, created embryos from those eggs, or proven the process is safe for clinical use. The company says the remaining work includes growing its stem-cell-derived follicles from the primordial stage to the antral stage, the point at which an IVF physician would retrieve an oocyte, and then validating the safety and quality of any future mature eggs.

That gap is the story. Conception's claim, if it holds up under independent scrutiny, moves in-vitro gametogenesis from a long-theorized reproductive technology toward a more concrete engineering problem: can a lab recreate enough of ovarian development to produce a usable human egg? The company says its answer is to build not just an egg-like cell, but a 3D ovarian environment around it. Its stated process starts with a blood sample, creates induced pluripotent stem cells, guides them toward primordial germ cells and ovarian helper cells, and combines them into mini-ovaries that mimic early ovarian tissue.

Conception says those mini-ovaries showed several markers it considers central: future egg cells progressing toward oogonia, cells entering meiosis, and fully stem-cell-derived follicles that pair early egg cells with support cells. The company also says it benchmarks the cells against an internal atlas of human ovary molecular data and uses deep learning models to compare development across stages. Those are company-supplied claims, not a peer-reviewed paper.

For Krisiloff, the milestone is also a validation of a founder thesis he has been pursuing since before Conception was widely known. The New Yorker reported in 2023 that Krisiloff first tweeted about in-vitro gametogenesis in 2017, while he was director of Y Combinator's nonprofit research arm, and that he had previously helped in OpenAI's early months. Krisiloff does not come from the usual biotech founder track. He studied Law, Letters, and Society at the University of Chicago, then built his way into hard science through startup institutions and research-heavy company formation.

Conception was founded in 2018 by Krisiloff, Pablo Hurtado Gonzalez (@pablohurt90), and Bianka Seres (@seres_bianka). Hurtado Gonzalez, a reproductive biochemist, met Krisiloff while visiting the lab of Katsuhiko Hayashi in Japan, according to The New Yorker. Seres had worked as an embryologist in a fertility clinic before earning a Ph.D. at Cambridge under meiosis researcher Melina Schuh. That mix explains Conception's unusual posture: a Silicon Valley company trying to solve a problem that normally advances through academic developmental biology.

The money followed that posture. The New Yorker reported that Conception had raised almost $40 million in venture capital as of 2023, with an initial $1 million from Hydrazine Capital and investors including Jaan Tallinn and Laura Deming. Krisiloff has since written on his own site about using patient, mission-aligned capital for long-running biotech bets, arguing that some founders should avoid structures that force short-term milestones onto research programs whose first product may be years away.

The scientific precedent is real but limited. Conception points to Hayashi's 2016 mouse work, in which skin cells were turned into induced pluripotent stem cells and then into usable eggs that produced healthy offspring. Mouse IVG, however, has consistently been easier than human IVG. Human egg development takes far longer, requires tight control of meiosis and chromosomal integrity, and introduces a safety bar that is fundamentally different from most therapeutics because any error can affect a child, not only a patient.

That is why Conception's announcement should be read as a research milestone, not a product launch. The company says future clinical use would require formal approval based on rigorous safety and efficacy data. Its website frames IVG as a medical therapy within existing regulatory systems, and the June update says deeper animal model development and safety validation remain ahead.

The strategic timing is also clear. Conception's post ends with a hiring push, and its jobs page lists roles in stem cell biology, RNA delivery, genome engineering, organoids, and related research functions in Berkeley. Publishing microscope images and a technical narrative gives Conception a recruiting asset in a field where the scarcest resource is not capital alone, but scientists willing to spend years on a high-risk developmental biology problem inside a startup.

The upside Conception is selling is enormous: more reproductive options for people with infertility, older prospective parents, cancer survivors who lost fertility, and potentially same-sex couples seeking genetically related children. The unsolved questions are equally large: whether these early oocytes can mature normally, whether chromosomal and epigenetic errors can be ruled out, whether regulators will permit clinical testing, and how society handles a technology that could make eggs abundant.

Conception has not answered those questions yet. What Krisiloff's team is claiming now is narrower and still consequential: it says it has built early human egg cells and follicle-like structures entirely from stem cells. In fertility technology, that is the difference between a speculative market and one where the hard parts can at least be tested in the lab.