MIT engineers have developed biological computational circuits capable of both remembering and responding to sequential input data. The group's work, which is described in this week's issue of Science, (http://science.sciencemag.org/content/353/6297/aad8559) represents a critical step in the progression of synthetic biology with the integration of DNA-based memory, in particular, pointing the way toward building large computational systems from biological components—computing devices that are living cells—and, ultimately, programming complex biological functions.