Our organs exhibit beautiful and complex shapes, which are precisely sculpted during embryonic development. A central question is how the physical shape of an organ emerges from the collective activity of its constituents – thousands of microscopic fluctuating biological cells. To address this question, we develop quantitative human stem-cell systems that undergo complex shape changes in response to minimal biochemical cues. Our goal is to understand how the interplay between biological regulation and mechanical phenomena determines organ shapes and how misregulation leads to human birth defec