This volume focuses exclusively on those endocytic processes that sequester proteins by a selective, receptor-mediated mechanism. In such an endocytic process, cell surface receptors specifically bind protein ligands and localize them to specialized invaginations of the plasma membrane. These regions are coated pits, so named because they are lined on the cytoplasmic face with an ordered array of the protein, clathrin. It is this 'coat' which provides their characteristic electron microscopic image. Subsequently, these regions pinch off to form coated vesicles which rapidly lose their 'coat'...