After a baby is born, special cells in tiny sacs start making milk. That milk has everything a new baby needs.
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At the ends of the milk tubes in the breast are tiny, round sacs. They are bunched together like grapes. Each sac is called an alveolus.
Milk-making cells line the inside of every sac, in a single layer around a hollow middle. Squeezy cells wrap around the outside.
After a baby is born, a hormone tells these cells to start making milk. They take things from the blood and turn them into milk, full of:
The milk drips into the hollow middle. When the baby feeds, the squeezy cells push it out into the tubes.
Milk also carries antibodies, tiny germ fighters that help protect a new baby from getting sick!
Press Make milk on the 3D model and watch the sac fill up.