This chapter discusses a history of the four agricultural revolutions that have permitted the human population to grow eightfold in the last 200 years. It describes how the structure of agricultural systems has evolved to meet the needs of an increasingly urban population. The fourth agricultural revolution is in progress at present applying digital control based on sensing and feedback control. These systems can also be used to minimize pollution from agricultural operations using multiple sensors in water and air and automatically controlling fertilizing operations. The digital technology and robotics also allow more small-scale peri-urban growing systems to reduce energy consumption in transport and bring fresh food to reduce the dependence on processed product that are believed to causing the obesity epidemic. New paradigms are needed in urban food supply and this chapter discusses some of the issues.