The immiscible cholesterol bilayer domain exists as an integral part of phospholipid bilayer membranes

► The cholesterol bilayer domain (CBD) is formed within the PCD as a coexisting domain. ► The organization of cholesterol in CBD differs significantly from that in cholesterol crystals. ► The EPR spin-labeling approach can discriminate and characterize the fraction of cholesterol that forms the CBD within the phospholipid bilayer.