This document provides an introduction to flexible housing. It discusses the origins of flexible housing in vernacular architecture and how social and technological changes led to its reemergence. Flexible housing aims to efficiently use space and adapt to changing user needs over time through adjustable interior layouts. Examples of flexible housing designs from Slovenia, the Netherlands, and Canada are described. Advantages include adaptability and efficient use of space, while disadvantages include potential increased costs. The document argues that flexible housing can help address issues of housing demand, affordability, and environmental impacts over the long term.