Active scalar equations play an important role in modeling fluids. Some of the best known examples of active scalars are the 2D Euler equation, the surface quasi-geostrophic (SQG) equation, and the Burgers equation. Most active scalars are nonlocal, making detailed analysis of their solutions challenging. I will review recent progress in this area. In particular, I will talk about a new recently developed method for analysis of active scalars, and its applications to studies of the regularity properties of solutions.