Milk refers to breast milk, which is produced by filtering the mother’s blood through the cells of the mammary glands. The fat, carbohydrates, vitamins and other nutrients in milk are taken in from the mother’s daily food, absorbed into the body through the bloodstream, and then filtered through the mammary cells to produce milk. Milk is absorbed and stored in the breast cells. After pregnancy, the body produces large amounts of estrogen and progesterone, which stimulate the development of the milk ducts and breast follicles, and also prepare for breastfeeding after birth. However, high levels of estrogen can inhibit milk production. After delivery, estrogen levels in the pregnant woman’s body drop rapidly and prolactin is synthesized in large quantities, so milk is synthesized and secreted. Therefore, milk comes from the mother’s blood, is produced in the breast cells and is discharged from the breasts. When the milk is not discharged well, it is easy to lead to the occurrence of milk stagnation and mastitis, so go to the hospital in time if you have any discomfort during the feeding process.