This document provides an overview of lean user research. It defines lean user research as low-cost methods of research used to either discover new ideas or validate existing work. Some examples of lean research methods include guerrilla testing, remote usability tests, intercept interviews, and A/B tests. The document discusses when lean research should be used, such as during design sprints or when questions arise. It also provides tips for how to effectively conduct lean research, including developing a plan, choosing a method, deciding on a sample size, and looking for patterns in results. The overall goal of lean research is to keep projects moving forward with minimum investment.