The lateral segregation of sphingomyelin in rigidliquid-ordered domains, surrounded by the fluid matrix of glycerophospholipids in the liquid-disordered phase,
was revealed. The heterogeneous distribution of glycolipids and glycoproteins was also observed
in the MFGM. A new model for the structure of the MFGM is proposed and discussed. The physical, chemical
and biological consequences, (i) of the differences in milk fat globule compositions according to their
size and (ii) of the specific structure of the MFGM due to sphingomyelin remain to be elucidated