Cells vary in shape and function, and while some are enormous (the ostrich egg, the largest single cell in the animal kingdom, averages six inches long and weighs about three pounds), most cells can only be seen with the help of a microscope. The smallest object the human naked eye can see is approximately one-tenth of a millimeter (0.10 mm) in size—roughly the thickness of a piece of paper (0.15 mm), and the approximate diameter diameter of a Southern white rhino egg (0.14 mm). Let's zoom in and see how other cells measure up.

Tracing Retrovirus through the Generations for Conservation and Health

Oak trees are iconic. They're also threatened with extinction. San Diego Zoo Wildlife Alliance is committed to protecting these keystone species.

If it looks like a duck, swims like an otter, and lays eggs, it's the platypus! Get an in-depth look at this freshwater-loving mammal.

Dive into the depths of water pollution issues and explore solutions for a more sustainable future.

Technology is making a powerful difference in the world of conservation, and our teams are at the forefront.

Leap Day only happens once every four years. Explore which extraordinary wildlife leap, jump, spring, and everything in between.

An unusual set of twins is duplicating hope for Przewalski's horses.

Regenerative medicine is proving to be a vital new therapeutic tool, offering vast new possibilities in veterinary care.

SDZWA and our partners use customized drones to collect killer whale breath and monitor orca health in real time.