The Mechanics of Making Milk What is Progesterone? How does progesterone relate to the milk making process? An overview of what you can expect. Hand Expressing Breast Milk Expressing milk by hand takes a little practice, but you should learn this useful skill. How Will My Breasts Know How Much Milk To Make? There are 4 different hormones that contribute to the making of milk. This video shows when each comes into play, and it’s role in the milk-making process.