Whether they’re in the brain or intestines, many tissues are programmed to bend, twist, and fold in specific ways. Now, scientists have harnessed this programming to create bowls, coils, and ripples out of living tissues that fold themselves up. To do so, the researchers started with plugs of cells taken from a connective tissue in mouse embryos. Called the mesenchyme, this tissue contains cell layers that either stretch or pinch together. When a pinching layer sits above a stretching layer, the two together cause the tissue to bend inward like a bow. Using a 3D printer, the researchers patterned sets of cell plugs in a culture dish filled with a gel containing tiny fibers made of extracellular matrix, a structural support naturally secreted by cells in the body. And by choosing which way they knew each set of cells would bend, they caused the overall collection of tissue to fold up into the variety of preprogrammed shapes seen in the image above, the team reports today in Developmental Cell. Eventually, researchers hope to use this strategy to engineer more natural tissues and organs able to replace those in lost in people because of age or disease.