This document summarizes research on factors that influence teacher learning through Lesson Study professional development. It explores how individual teacher characteristics, group dynamics, and school environment can support or constrain learning. Three teachers were interviewed about their experiences. Valsiner's Zone Theory is used as a framework, identifying the Zone of Proximal Development (individual characteristics), Zone of Promoted Actions (group factors), and Zone of Free Movement (school environment) as influencing teachers' learning. Key factors discussed include teachers' beliefs, motivation, collaboration, group atmosphere, and school policies.