Cells implement functions through the computation of biological information that is often mediated by genetic regulatory networks. To reprogram cells with novel capabilities, a vast set of synthetic gene circuits has recently been created. These include simple modules, such as feedback circuits, feed-forward loops, ultrasensitive networks, band-pass filters, logic gate operators and others, with each carrying a specific information processing functionality. More advanced cellular computation can also be achieved by assembling multiple simple processing modules into integrated computational cores. Further, when coupled with other modules such as sensors and actuators, integrated processing circuits enable sophisticated biological functionalities at both intra- and intercellular levels. Engineered genetic information processing circuits are transforming our ability to program cells, offering us extraordinary opportunities to explore biological mechanisms and to address real-world challenges.