Fig. 1.

Interrogating Brownian motion in the ‘black box’ of the cell. A labeled (white) particle’s motion is followed in (top) the two-dimensional (2D) plane of the cell membrane (shown here as composed of various lipid domains and integral membrane proteins in contact extracellularly with polysaccharides and intracellularly with the cortical cytoskeleton) and (bottom) in the three-dimensional (3D) space of the cell cytosol (shown here as composed of various soluble proteins, cytoskeletal elements, nucleic acids, lipids, carbohydrates and inorganic ions)