Surfactants [local] are compounds that contain hydrophilic and hydrophobic components.

Surfactants are thought to form micelles:

Surfactants can form bilayers [local], many of which have extreme importance in biology because they constitute cell membranes. Lipid bilayers.

Vesicles are spheres in which monolayers or bilayers of surfactant material form the surface (membrane). This has the effect of separating the liquid (solution) on the outside of the vesicle from that on the inside. Vesicles can be prepared by extrusion [local]. A liposome is a synthetic membrane vesicle made from phospholipids and used for studies of membrane-defined events such as transport, or for the delivery of substances to a cell. In a synapse, for example (functional connection between two nerve cells), the neurotransmitters often are released into the synaptic cleft (space) by extruding liposomes filled with those chemicals.