The research field of interorganelle contacts is one of the most rapidly growing areas of modern cell biology. It is becoming clear that many, if not all, organelles form membrane contact sites (MCS) with other components of the cell. The term ‘MCS’ broadly describes a physical interaction between two organelles, occurring at specialized subdomains of the given organelle and involved in multiple facets of the biology of the two organelles that are juxtaposed. MCS discovery forced cell biologists to reconsider the way organelles are studied, introducing the concept that heterotypic organelle interaction allows functions that individual organelles would otherwise be unable to perform and forcing them to think in terms of compartmentalized metabolism and signaling.