New forms of materials can often enable new device and system applications.  In this talk, I will discuss our studies on atomically-thin-body (ATB) semiconducting membranes for two applications.  Firstly, because of their ultrathin nature and excellent mechanical flexibility, ATB Si membrane leads to large scale, high resolution soft electrode arrays, enabling unprecedented bio-signal mapping capabilities for both the heart and brain.  Secondly, due to their extreme miniaturization, ATB semiconducting channels are also ultra-sensitive to external electrostatic perturbations, enabling sub-ppt-level chemical sensing.  At the end of my talk, I will introduce our recent concept on semiconductor nanomeshes. By making an ATB Si into homogeneous nanomeshes, we achieve high mobility semiconductors that are intrinsically stretchable to conventional microelectronic layouts.  Together, our work demonstrates that ATB semiconducting membrane is a unique approach to transforming conventional electronics for emerging applications.