Scanning electron micrograph (SEM) of Casein micelles. Casein micelles are minute protein globules that continually collide and ricochet in fresh milk. Their free path is about 3 micelle diameters. Under the effects of enzymes (chymosis) or acids the proteins coagulate. This image shows the beginning of coagulation, where the casein micelles begin to form clusters. The minute particles on the base are submicellart casein. (Image width: 0.61 micrometer, bar: 0.1 micrometer.)