The digital video sequences presented in this section visualize the dynamic activity of endosomes, which were targeted with mCherry fused to the early endosomal marker Rab5a, in relation to the microtubule network, tagged with mEmerald fused to tubulin. Endosomes are formed via a complex family of processes collectively known as endocytosis. There are three primary types of endocytosis: pinocytosis, phagocytosis, and receptor mediated endocytosis. Once endosomes are released into the cytoplasm of a cell, their activity is varied and typically entails multiple steps before completion.