The goal of building biocomputers that can sense, analyze and control molecular information in live cells has long motivated DNA nanotechnology research. But so far most work on DNA strand displacement circuits has been performed in cell free settings because of the challenges associated with operating in the cellular environment, where exogenously delivered nucleic acids are rapidly degraded or sequestered. In recent work, we took a first step towards adapting strand displacement technology to the cellular environment and demonstrated nucleic acid logic gates that work in mammalian cells.