This document discusses using microsimulation models for policy evaluation. It begins by outlining the objectives of policy evaluation, such as understanding the costs, distributional impacts, and behavioral responses to potential policies. It then discusses the complexity involved in modeling policies given variability in populations. Different types of microsimulation models are described, including hypothetical, static, behavioral, dynamic, spatial, and cross-country models. Examples are provided of how various microsimulation models have been used to evaluate policies related to issues like unemployment traps, pension reform, and the impact of macroeconomic shocks. The challenges of building and implementing microsimulation models are also addressed.