Calcium plays an important role in many biological processes. At first, it might seem that the most important role of calcium in biology is a structural one, and indeed it may be argued that this is true. Hydroxyapatite, a co-crystal of calcium, phosphate, and hydroxide ions, forms the matrix of tooth enamel, the hardest substance in the human body. Calcium phosphate is also responsible for the rigidity of bone, and the deposition of this matrix in bone is a very tightly controlled biological process (1). In fact, the vast majority of calcium (more than 99%) is immobilized in bones and teeth in humans. Poor diet or improper regulation of calcium deposition can lead to diseases such as childhood rickets or osteoporosis in older adults. Moreover, calcium is also important structurally in other organisms; for example, calcium carbonate is the major component of egg shells and also of the exoskeleton of animals such as mollusks and barnacles. Nutritionally, calcium is found in many foods, but of course the major source in most human diets is dairy products. In milk, a predominant class of proteins is the caseins, which function to solubulize calcium phosphate microgranules by surrounding them in a micellar structure (2), providing an important mineral nutrient in liquid form.