Synthetic lipid bilayers have long been used as models of cell membranes. The compositional asymmetry in the eukaryotic plasma membrane is a key chemical characteristic of this membrane that has traditionally been difficult to reproduce in synthetic systems. In this chapter, we describe recent technologies for fabricating compositionally asymmetric giant unilamellar lipid vesicles (GUVs) and provide detailed protocols for a microfluidic-based fabrication technique.