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).