Through a comparative case study, Sheridan and colleagues explore how makerspaces may function as learning environments. Drawing on field observations, interviews, and analysis of artifacts, videos, and other documents, the authors describe features of three makerspaces and how participants learn and develop through complex design and making practices. They describe how the makerspaces help individuals identify problems, build models, learn and apply skills, revise ideas, and share new knowledge with others. The authors conclude with a discussion of the implications of their findings for this emergent field.