Breastmilk comes from the breasts and the nutrients in it come from the mother’s blood. After pregnancy, the mother’s body produces a large amount of estrogen and progesterone, which stimulates the development of mammary gland ducts and mammary gland follicles in preparation for lactation after delivery, but a large amount of estrogen and progesterone inhibits milk production. After delivery, the level of estrogen and progesterone in the body drops rapidly, prolactin is secreted in large quantities to promote milk synthesis and secretion, and the newborn sucks on the nipple and milk begins to be secreted. The fat, carbohydrates, vitamins and other nutrients in breast milk mainly come from the mother’s blood, which is filtered through the mammary cells to generate milk, which is absorbed and stored in the mammary cells. Human milk is the best natural food to satisfy the physiological and psychological development of infants, and has an irreplaceable role in the healthy growth and development of infants. Therefore, breast milk comes from the mother’s blood, is produced in the mammary cells, and is excreted from the breasts. When breastmilk is not discharged well, it can easily lead to milk stagnation and mastitis, so go to the hospital in time if there is any discomfort in the breastfeeding process.