About 40 years ago, Louise Brown, the first human created using in vitro fertilization, was conceived in a petri dish. Not long after her birth, Leon Kass, a prominent biologist and ethicist at the University of Chicago, wrung his hands about the then-­revolutionary technology of joining sperm and egg outside the body. The mere existence of the baby girl, he wrote in an article, called into question “the idea of the humanness of our human life and the meaning of our embodiment, our sexual being, and our relation to ancestors and descendants.” The editors of Nova magazine suggested in vitro fertilization was “the biggest threat since the atom bomb.” The American Medical Association wanted to halt research altogether.

Yet a funny thing happened, or didn’t, in the decades that followed: Millions of babies were conceived using IVF. They were born healthy and perfectly normal babies, and they grew to become healthy and perfectly normal adults. Brown is one of them. She lives in Bristol, England, and works as a clerk for a sea freight company. She’s married and has two healthy boys. Everyone is doing fine.

Nothing so excites the forces of reaction and revolution like changes in human reproduction. When our ideas of sex are nudged aside by technologies, we become especially agitated. Some loathe the new possibilities and call for restrictions or bans; others claim untrammeled rights to the new thing. Eventually, almost everyone settles down, and the changes, no matter how implausible they once seemed, become part of who we are.

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April 2018. Subscribe to WIRED. Nik Mirus

We are now on the brink of another revolution in reproduction, one that could make IVF look quaint. Through an emerging technology called in vitro gametogenesis (or IVG), scientists are learning how to convert adult human cells—taken perhaps from the inside of a cheek or from a piece of skin on the arm—into artificial gametes, lab-made eggs and sperm, that could be combined to create an embryo and then be implanted in a womb. For the infertile or people having trouble conceiving, it would be a huge breakthrough. Even adults with no sperm or eggs could conceivably become biological parents.

In the future, new kinds of families might become possible: a child could have a single biological parent because an individual could theoretically make both their own eggs and sperm; a same-sex couple could have a child who is biologically related to both of them; or a grieving widow might use fresh hair follicles from a dead spouse’s brush to have a child her late husband didn’t live to see.

At the same time, modern gene-editing technologies such as Crispr-Cas9 would make it relatively easy to repair, add, or remove genes during the IVG process, eliminating diseases or conferring advantages that would ripple through a child’s genome. This all may sound like science fiction, but to those following the research, the combination of IVG and gene editing appears highly likely, if not inevitable. Eli Adashi, who was dean of medicine at Brown University and has written about the policy challenges of IVG, is astounded by what researchers have achieved so far. “It’s mind-boggling,” he says, although he cautions that popular understanding of the technology has not kept pace with the speed of the advances: “The public is almost entirely unaware of these technologies, and before they become broadly feasible, a conversation needs to begin.”

The story of artificial gametes truly begins in 2006, when a Japanese researcher named Shinya Yamanaka reported that he had induced adult mouse cells into becoming pluripotent stem cells. A year later, he demonstrated that he could do the same with human cells. Unlike most other cells, which are coded to perform specific, dedicated tasks, pluripotent stem cells can develop into any type of cell at all, making them invaluable for researchers studying human development and the origins of diseases. (They are also invaluable to humans: Embryos are composed of stem cells, and babies are the products of their maturation.) Before Yamanaka’s breakthrough, researchers who wanted to work with stem cells had to extract them from embryos discarded during IVF or from eggs that had been harvested from women and later fertilized; in both cases, the embryos were destroyed in the process of isolating the stem cells. The process was expensive, controversial, and subject to intense government oversight in the United States. After Yamanaka’s discovery, scientists possessed a virtually inexhaustible supply of these so-called induced pluripotent stem cells (or iPSCs), and all over the world, they have since been trying to replicate each stage of cellular development, refining the recipes that can coax stem cells to become one cell or another.