A real-time view of life within 100 nm of the plasma membrane

The plasma membrane is a two-dimensional compartment that relays most biolo gical signals sent or received by a cell. Signalling involves membrane rece ptors and their associated enzyme cascades as well as organelles such as ex ocytic and endocytic vesicles. Advances in light microscope design, new org anelle-specific vital stains and fluorescent proteins have renewed the inte rest in evanescent field fluorescence microscopy, a method uniquely suited to image the plasma membrane with its associated organelles and macromolecu les in living cells. The method shows even the smallest vesicles made by ce lls, and can image the dynamics of single protein molecules.