In a lab at Cincinnati Children’s Hospital Medical Center, a series of small blobs sit in a Petri dish. They’re white, hollow, and the size of small peas.

They are stomachs.

More precisely, they are lab-grown model stomachs. Graduate student Kyle McCracken worked out how to make them by coaxing stem cells into producing stomach tissue—a feat that no one had yet managed. The results look like simple baubles, but the growing cells somehow organise themselves into the classic architecture of an actual stomach. They make the right layers, folds, and pockets, and they switch on the usual genes. “They’re not mixed bags of cells,” says Jim Wells, who led the study. “They look shockingly like mini-stomachs.”

These creations, known as gastric