Criminology tries to understand and explain crime and criminal behavior. Each criminal event is an opportune cross-product of law, offender motivation, and target characteristic arrayed on an environmental backcloth at a particular point in space-time. Each element in the criminal event has some historical trajectory shaped by past experience and future intention, by the routine activities and rhythms of life, and by the constraints of the environment. A theory of crime must be flexible, able to explain criminal events against diverse variations in the backcloth. To be of much value, a theory must make it possible to recognize and understand both individual and aggregate patterns of behavior at many levels of resolution. Routine activities of potential offenders generally define both the areas where and the times when they are likely to commit a crime. The routine activities of potential victims also shape the patterns of crimes.