This issue goes small, investigating the very large potential of organoids—miniature recreations of human organs—in understanding disease and fine-tuning treatments. The intersection of nanotechnology and medicine is also explored, and there’s a close-up view of attempts to build a bionic pancreas, which could make it simpler and safer for diabetics to manage their disease. In the policy realm, we consider arguments about whether surgeons should “correct” babies’ ambiguous sex organs.