Just one


A scanning electron microscope image of a single red blood cell on the tip of a needle.

Stress affects children too. Children who grow up in stressful situations have shorter telomeres, an early sign of genetic ageing that makes them vulnerable to diseases such as cancer. Telomeres shrink when cells divide, but when they get too short, the cell can’t divide and dies.

Bdellovibrio bacteriovorus is a bacterium that attacks other bacteria. It can charge its prey at speeds of up to 100 micrometers per second, comparable to a human running 600 kilometers per hour. It then bores into its hapless victim by spinning at 100 revolutions per second. Most bacteria aren't quite that fast, but they can move by whipping flagella or by spiraling through their environment.

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As soon as we're born, we're destined to age. Some of us age gracefully - we enjoy years of youthfulness - while others experience hair loss, wrinkles, and greying earlier than expected.

Found in the core of each hair, a pigment known as melanin gives rise to a person's hair color. This universal pigment is also found in our skin and eyes, giving use our unique physical traits. Dark and light versions of melanin - eumelanin and phaeomelanin, respectively - combine in various combinations to create all natural hair colors.

Melanin itself is the product of a specialized cell, the melanocyte, which is found in each hair follicle, from which the hair grows. As hair grows, the melanocyte injects melanin into the hair cells, which contain the s ...