(A) Sketch of the heterogeneous cell membrane composed of different lipids, proteins and other molecules. Dynamic compartmentalization occurs at different spatiotemporal scales originating from lipid rafts, interactions with the extracellular matrix and glycocalyx from the outside, and also patterned by the cortical actin cytoskeleton on the cell inside. (B) To probe the spatiotemporal cell organization of the membrane, lipids and/or proteins of interest can be fluorescently tagged and their diffusion over time can be recorded. Depending on their location and time point, the diffusion behavior may be freely random, confined by the occurrence of compartments or hindered by their partitioning into domains.