Stars form in clusters, and many of these stars form in binary and multiple systems. Simulations of the evolution of slightly turbulent cores show that stars form in small-N groups. Brown dwarfs can be formed by ejections from these groups, and the remaining binary and multiple systems have properties very similar to observations. We now have a theory for the origin of the IMF from a core mass distribution and I'll show that the unusual IMF of Taurus can be explained if all the stars formed in 5 solar mass cores.