Wearable device that matches the soft human body represents an important trend for bio-integration; the resulting search for pliable electronic materials calls for strategies to bridge the gap between hard and soft – among which advanced engineering of the geometry and architecture of materials presents unique opportunities. A prominent example of materials engineering is that the compressive straining of an elastic substrate can be used to fabricate previously inaccessible classes of 3D structures in monocrystalline materials. Conversely, rationally designed 2D geometries can buckle to form 3D layouts to accommodate tensile strain, resulting in unprecedented stretchability. This enables a series of device possibilities in stretchable electronics, including lithium ion batteries with record stretchability and integrated soft health monitoring systems.