Architecture is increasingly called upon to invent new scenarios, ecology-friendly, energy-efficient and resilient, within which the dynamics between the built and the natural environments can unfold. The emphasis is being placed on the architectural envelope, as design continues to push the upper limit on its thinness, lightness and permeability, in a way that this particular component is progressively conceptualised as a breathing, living, active element. Moving between theory and practice, this book explores the instances where the architectural discourse and practice have intersected with the organic metaphor, with notions associated with the anatomy of the skin and the physiological process of breathing, exploring new connections between inside and outside, space and structure, nature and artifice. In this context, it conceives of the envelope as a complex architectural system - one that intersects with technological advances, with knowledge deriving from the sciences, with the changing climatic conditions - drawing attention to issues of mediation between architecture and the environment at large.