Week 2: your baby is the size of stardust

Still stardust. Ovulation happens around now, and if a sperm meets that egg, that distant glimmer becomes a single cell and the most ambitious construction project of your life begins.

Weeks 1 and 2 are really one long overture, which is why they share a picture: there is no embryo here yet, only potential, an egg getting ready for its close-up, and the same single point of light.

If fertilisation happens, that first cell is about 0.1 mm across, roughly the width of a human hair. Everything that will become a nervous system, a heartbeat, ten fingers, and a personality fits inside a dot smaller than this period. Nature packs light for the journey.

Meanwhile, inside you

Before your baby is the size of any animal, they are the size of nothing at all, and made of everything. Next week we start meeting the animals.