Because the acyl chain structures of sphingolipids are largely saturated and longer than the acyl chains of most phospholipids, the lipids are highly extended and tightly packed in rafts .  In fact, the differential packing ability of sphingolipids and phospholipids leads to phase separation in the plane of membranes. 

One can look at three phases of lipid in membrane:

• the liquid ordered state (lo)

• the liquid disordered state (ld)

• the gel-phase (lc)

The lc phase is dominant where lipids are tightly packed. High degree of cholesterol gives the lipid layer more flexibility and loser packing, forming microdomains in lo phase. The ld phase is characterized by shorter and more unsaturated phospholipid in the membrane layer.  The formations of lipid rafts are highly dynamic and the lipids have high degree of lateral mobility.

Today, many proteins have been characterised which are found to associate preferentially with lipid rafts through a so-called glycosyl phosphatidyl inositol anchor (GPI-linked).  Other proteins which are linked to the membrane through saturated acyl chains or through acylation with palmitate and myristate have been shown to be generally associate with other microdomains. 

The main methods for the isolation of lipid rafts have used their insolubility in non-ionic detergents, mainly Triton X-100, followed by sucrose density gradient.  However, many disputes have risen regarding their existence in vivo because the use of detergent witch has been showed by the usage of different detergent, giving different result in protein composition.  A Keystone Symposium on Lipid Rafts and Cell Function in 2006 brought together biophysicists, biochemists, and cell biologists to discuss the structure and function of lipid rafts.  Their conclusion was that lipid rafts do indeed exist and agreed on a consensus definition:

"Membrane rafts are small (10-200 nm), heterogeneous, highly dynamic, sterol- and sphingolipid-enriched domains that compartmentalize cellular processes. Small rafts can sometimes be stabilized to form larger platforms through protein-protein and protein-lipid interactions."