Endocytosis is responsible for the movement of materials from outside the cell into the cytoplasm. Cells use phagocytosis to engulf large particulate material. The case study, “Following the Fate of a Phagosome,” examines work by C.D. Blanchette, Y.-H. Woo, C. Thomas, N. Shen, T.A. Sulchek, and A.L. Hiddessen (Decoupling internalization, acidification and phagosomal-endosomal/lysosomal fusion during phagocytosis of InlA coated beads in epithelial cells. PLoS One. 2009;4:e6056) investigating the internalization, acidification, and fusion steps of phagocytosis. Receptor-mediated endocytosis is responsible for the uptake of extracellular materials based on receptor ligand binding. This type of endocytosis is associated with the formation of clathrin-coated pits that become clathrin-coated vesicles. The work by W. Boll, A. Gallusser, and T. Kirchhausen (Role of the regulatory domain of the EGF-receptor cytoplasmic tail in selective binding of the clathrin-associated complex AP-2. Curr Biol. 1995;5:1168–1178) is used in the case study, “Catching a Receptor by the Tail,” to investigate the role of the receptor in clathrin coat assembly. The case study, “Can Clathrin Bend a Membrane?” evaluates data from work by P.N. Dannhauser and E.J. Ungewickell (Reconstitution of clathrin-coated bud and vesicle formation with minimal components. Nat Cell Biol. 2012;14:634–639) which supports the idea that clathrin alone can cause membrane deformation. Finally, the case study, “Modeling Membrane Fission,” looks at the role of the protein dynamin in endocytosis (Pucadyil TJ, Schmid SL. Real-time visualization of dynamin-catalyzed membrane fission and vesicle release. Cell. 2008;135:1263–1275).