700 million years ago, a remarkable creature emerged for the first time. Though it may not have been much to look at by today’s standards, the animal had a front and a back, a top and a bottom. This ...

One of the biggest quests in biology is understanding how every cell in an animal's body carries an identical genome yet still gives rise to a kaleidoscope of different cell types and tissues. A ...

A visualization of Tiktaalik roseae, an extinct aquatic animal with fossils that shed light on the evolution of land animals from marine animals millions of years ago. Nobu Tamura via Wikimedia ...

Embryonic germ layers are the fundamental organizing principle in animal development. They provide the structural basis from which tissues and organs arise. During early embryogenesis, cells divide to ...