A presentation of the most fundamental features of the biology of the mammary gland, a unique model of an organ capable of an abundant synthesis of proteins: endocrinology of lactation, role of prolactin, genetics and protein synthesis, immunology and the mammary gland, nutrition and dairy products. Readership: students, teachers, researchers, health and agriculture professionals. Lactation Biology was first published in French in 1993. The English version is not merely a translation: it has been updated by the author.