This document introduces the lean canvas tool for brainstorming business models. It is divided into 9 segments and is used to sketch multiple business model hypotheses targeting different customer segments. The lean canvas prioritizes problems, customers, and unique value propositions. It provides a simple format to test business model assumptions and track learning through iteration. The document outlines 3 steps: 1) brainstorm customers, 2) sketch multiple canvases, 3) prioritize where to start based on factors like customer pain, ease of reach, price and market size. Compared to lengthy business reports, the lean canvas is portable, flexible, and fosters creativity through its concise, problem-solution focused approach.