Simple microscopic dynamics can capture essential aspects of physics, such as locality, microscopic reversibility, and conservation laws. From such simple microscopic dynamics we can observe the emergence of complex macroscopic physical phenomena. I will first discuss a well known microscopic model of particle collisions which, in the macroscopic limit, obeys the equations of hydrodynamics. Then I will illustrate the use of such models as a laboratory for studying nonequilibrium thermodynamics via a model of pattern formation in a closed system. In this model we observe the initial growth of bushy fractal clusters (resembling frost on a window pane), then the slow approach to thermodynamic equilibrium during which the cluster structures anneal and undergo a transition to structures resembling branched polymers. Finally, I will discuss computation in these microscopic models of physics, showing that this model of cluster growth is computationally universal.