Membranes - porous biological interfaces which regulate flows between one zone and another - are the foundational image for an issue guest-edited by Granta contributor and best-selling novelist Rana Dasgupta. Featuring new poetry from Andrew McMillan and Tishani Doshi, photography from Ruchir Joshi, Arturo Soto Gutierrez, Monica de la Torre and Anita Khemka, as well as cutting-edge fiction and thought-provoking essays: Fatin Abbas on the border between Sudan and South Sudan Lydia Davis on faultlines in families Mark Doty on homelessness in New York City Anouchka Grose on infidelity and the idea of the unwanted third Daisy Hildyard on membranes in the human body Adam Jasper on Christian Enzensberger and 'smut' Kapka Kassabova on lakes and Europe Anita Roy on the newt Eyal Weizman on contemporary architectural strategies for repelling and dividing people