The nanoscale dimensions, sensitive electronic control, and flexible architecture of new generations of nanomaterials and nanofabrication techniques hold immense promise not only for electronic devices, but also biological interfaces. As the size scales of these materials approach biological species, interfaces with characteristics designed to emulate their nanoscale biological counterparts are becoming possible. These new systems have higher biocompatibility, functionality, and lower cell toxicity than their microscale predecessors. While stellar examples have been demonstrated for biomolecular detection and imaging, exciting new possibilities for long-term integration and dynamic stimulation are now emerging, including protein activation, membrane integration and intracellular delivery. These tailored interfaces may lead to improved regenerative medicine, gene therapy and neural prosthetics.