The secretory transport capacity of Giardia is perfectly adapted to its changing environment and is able to deploy essential protective surface coats as well as molecules, which act on host epithelia. The lumen-dwelling trophozoites take up nutrients by bulk endocytosis through peripheral vesicles or by receptor-mediated transport. Despite its versatility and fidelity, the giardial trafficking machinery appears to be the product of a general secondary reduction process that led to minimization of all components identified so far. Giardia is emerging as a model for the investigation of synthesis, transport, and assembly of highly effective biopolymers, a hallmark of all perorally transmitted protozoan and metazoan parasites. The cell biology of this simplified and highly derived organism allows unique insights into the function of minimal systems, which can be studied in an uncluttered cellular environment.