a | Lipid raft domains are small, highly dynamic and transient plasma membrane entities enriched in saturated phosho-, sphingo- and glycolipids, cholesterol, lipidated proteins and glycosylphosphatidylinositol (GPI)-anchored proteins. Enrichment in these hydrophobic components endows lipid rafts with distinct physical properties, including increased lipid packing and order, and decreased fluidity. In addition to membrane components, cortical actin plays an active role in domain maintenance and remodelling. Further, membrane lipids are asymmetrically distributed in the inner and outer leaflets, and this may further impact membrane organization. b | It is likely that membrane organization is not binary (i.e. highly specified raft and non-raft regions), but rather consists of various raft-like and non-raft domains with distinct compositions and properties.