The breastfeeding process starts mid way through pregnancy when your body begins to make your fire milk, colostrum. Colostrum is a thick yellow fluid that is a concentrated source of antibodies, protein, fat. During pregnancy you have high levels of prolactin and progesterone to keep milk supply low (Lactogenesis I). With the birth of your placenta, your progesterone levels drop drastically allowing for the transition of the next stage of your milk over the next 2-3 days(Lactogenesis II). Up until this point your breast milk was driven by hormones but now it will be driven by supply and demand (Lactogenesis III).