causal set theory is an approach to quantum gravity based on the idea that spacetime is fundamentally discrete and lorentz invariant. structurally, a causal set is a locally finite partial order, or a transitive dag (directed acyclic graph). after a brief introduction to the idea, i will give an overview of some of the recent research activity in causal sets. some topics i hope to touch on are: measures of discrete geometry (e.g. distance, curvature,…), dynamics on causal sets (e.g. classical and quantum fields), and phenomenology from causal sets (e.g. dark energy).