Changes in the junctions between nerve cells determine how well a bird will learn to sing. Regular change in these junctions helps the bird remember the song of its species, which it needs to learn to reproduce that song. Study could explain why older people have such trouble learning a new language.

New video captures AIDS moving inside immune cells: HIV enters pods that form on the surface, then jumps across into a healthy immune cell that is now doomed to spread HIV — and die.

Scientists learn to make human embryonic stem cells without using eggs, embryos, or legal hassles. Adding four genes to skin cells did the trick.

Survive the vaccination routine? That’s no fun for anyone — parent or child.

Computer graphics and microbiology unite as scientists build complex digital models of cellular machinery to view a microscopic world in powerful new ways.