The Lichen House nestles within the fog and oaks in the hills above California’s Sonoma Valley. The free-ranging branches of the site’s mature live and coastal oak trees support veils of draping Ramalina Lichen that filter sunlight, capture moisture and nutrients for their hosts, and remove pollutants from the air through photosynthesis. A hypersensitive organism, lichen retreats or dies in adverse or contaminated environments but quickly expands its net with conditions advantageous for growth. It is a bellwether for the environmental health of this unique microclimate. This precise relationship between lichen and host provides inspiration for an architecture specifically tailored to its site – both as a response to it and as an augmentation of its best attributes. The Lichen House works in concert with nature’s mechanisms, not to mimic them blindly, but to expand our understanding and experience of them through architecture. Lichens grow and spread to produce their own food using sunlight – they do not feed on or harm the trees they inhabit. They establish an ethos for design inspiring symbiotic, rather than dominant, relationships between built and unbuilt worlds – one that mirrors the gesture and fluidity of movement in the architecture.