On the second day of the Second International Summit on Human Genome Editing, the last session before lunch was already running long. But the crowd crammed into the Lee Shau Kee Lecture Centre at the University of Hong Kong wasn’t budging. Neither were the 5,500 people around the world glued to their live video feeds. Everyone was waiting to hear from the the final speaker, the man who says he helped make the world’s first gene-edited babies.

That man is He Jiankui, the Chinese-born, American-trained biophysicist who claims to have Crispr’d a pair of twin baby girls.

LEARN MORE The WIRED Guide to Crispr

Robin Lovell-Badge, a biologist at the Francis Crick Institute in the UK, took to the podium to introduce the controversial speaker. Lovell-Badge reminded everyone that the National Academy of the Sciences, the global non-governmental science panel that helped convene this summit, did not know in advance about He’s work. “He sent me the slides he was going to show in this session and they did not include any of the work he was going to talk about,” said Lovell-Badge. “Nothing involving human embryos that were implanted.”

But after MIT Technology Review broke the news of He’s covert trials two days ago, He’s session at this event became the object of intense fascination. Folks following along on Twitter wondered if He would show at all. And for one long, agonizing minute after Lovell-Badge welcomed He to the stage, it looked like he might not. When He at last appeared, he began to deliver a different talk, packed with details about what he’d been up to.

For the last two years, He has been working in secret, skirting ethical and scientific codes of conduct, and possibly even some laws, to make biological history. On Wednesday morning, Hong Kong time, he revealed to the world just how he did it. It will take scientists days to parse the 59 data-dense slides that describe He’s methods and results. Only then will a fuller picture begin to emerge about just how safe and effective the experiment was. But in the meantime, He still gave the rest of us plenty to think about.

Like the fact that Lulu and Nana, the twin girls, aren’t the only children He’s group has Crispr’d. When pressed on the number of implantations that have taken place so far, the scientist disclosed that there is another potential pregnancy involving a gene-edited embryo. He hesitated to answer the question because the pregnancy is in an early stage. His research team has so far injected Crispr systems into 31 embryos that have developed to the blastocyst stage. He said 70 percent of them were successfully edited and await further screening and implantation in five remaining couples. But now that’s all on hold. “The trial is paused due to the current situation,” said He.

He is now under investigation by his own university, and other legal bodies in China.

After He’s presentation, he took questions from the audience and the moderators, including Lovell-Badge and Matthew Porteus, a Stanford researcher and the scientific founder of Crispr Therapeutics, a company developing Crispr-based drugs to treat genetic diseases. Throughout, He remained calm and thoughtful, if not always fully forthcoming.

At one point, Harvard biochemist David Liu questioned the unmet medical need that He said his experiments were addressing. He recruited couples where the mother is HIV-negative and the father HIV-positive, editing their embryos to bestow them with a rare but natural trait—the ability to resist HIV infections. Given that there are ways to make sure HIV-positive parents don’t transmit their disease to their babies without altering their DNA, Liu asked He to “describe the unmet medical need, not of HIV in general, but of these patients in particular.”