Abstract: Active matter consists of particles that do work on their environment, for example by propelling themselves through a solvent. Fluids made from many interacting self-propelled particles have become popular as models of non-equilibrium matter: they are challenging for theory and computation because their steady states cannot be derived by minimizing a free energy, nor any other thermodynamic potential. I will discuss their behaviour on large length and time scales, including possibilities for dynamical pattern formation, glassy behavior, and surface phase transitions (wetting).