Aging affects the whole body, from the brain to the muscles.
Scientists are always looking for ways to slow it down.
Recently they studied a substance found in edible sea squirts, simple animals from the ocean.
When they gave this substance to older mice, the results were surprising.
The mice showed clear improvements in memory and muscle strength.
In other words, several signs of aging were reversed.
However, the researchers warn that this is still very early work.
So far it has only been tested in animals, and human use is a long way off.