Neuron Development in Human Embryos
University Hospitals, Tiny Fox Lab

At birth, a baby’s brain contains 100 billion neurons, roughly as many nerve cells as there are stars in the Milky Way, and almost all the neurons the brain will ever have. The brain starts forming prenatally, about three weeks after conception. Starting in the third trimester, the brain eliminates unnecessary neurons via a process known as apoptosis.Tiny Fox Lab Facts

Preview photo credit: University Hospitals
Source: https://sites.duke.edu/apep/module-5-alcohol-and-babies/explore-more/normal-brain-development/