This unit describes protocols for making giant unilamellar vesicles (GUVs) based on rehydration of dried lipid films. These model membranes are useful for determining the impact of membrane and membrane-binding components on lipid bilayer stiffness and phase behavior. Due to their large size, they are especially amenable to studies using fluorescence and light microscopy, and may also be manipulated for mechanical measurements with optical traps or micropipets. In addition to their use in encapsulation, GUVs have proven to be useful model systems for studying many cellular processes, including tubulation, budding, and fusion, as well as peptide insertion. The introduction of enzymes or proteins can result in reorganization, leading to such diverse behavior as vesicle aggregation, fusion, and fission.