Small angle neutron scattering will be used in combination with contrast variation as a non-invasive method to detect the presence and size formation of lipid microdomains or rafts in vesicles as a function of lipid composition, temperature and vesicle size. The raft forming lipid mixture to be used is the ternary lipid system comprising of palmitoyl sphingomyelin/palmitoyloleylphosphatdylcholine/cholesterol. This ternary mixture is a particularly good model for lipid microdomains as the plasma membrane is rich in cholesterol and sphingolipids as well as phospholipid, while in addition its phase behaviour is well established. Once the temperature of raft formation is determined, the evoluation of the rafts in terms of size will be established after rapidly cooling the sample using SANS2D exploiting event mode.