How does the reproductive system work?

Two small sets of organs, deep in the pelvis, can start a whole new person. Ovaries store eggs and release about one a month into the fallopian tubes, which lead to the uterus. Testes make about 100 million sperm a day, which mature in the epididymis and travel up the vas deferens.

Read how it works: How does the reproductive system work? · The history of the reproductive system · More boxes on Glassbox

Chapters in this interactive model

1. The organs that make new life: Two sets of organs, deep in the pelvis, each with one job: to make and move the cells that start a baby.
2. Puberty: when the brain says "start": A tiny signal from the brain sets off years of change, at a different time for everyone.
3. The menstrual cycle: a monthly clock: About once a month, an egg ripens and the uterus gets ready. If no baby starts, the lining is shed and the clock restarts.
4. Fertilisation: two cells become one: In the fallopian tube, one sperm joins one egg. The new cell divides and divides, and settles into the uterus.
5. Nine months: from one cell to a baby: About 40 weeks of growth, fed through the placenta and the umbilical cord.
6. Looking after it, and each other: Check-ups, period health, infections and fertility, and the respect every body deserves.