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This is the VOA Special English ENVIRONMENT REPORT.

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Geckos are small lizards that live in warm climates. These lizards can stick to any surface. For example, geckos can climb up walls and across the top of a room. Scientists have studied the little lizards for hundreds of years to learn the secret of how they stick to things. Now, they say they have finally solved the mystery. They hope the finding will help them develop powerful materials that hold things together.

A team of American biologists and engineers carried out the study. Their findings were published in the Proceedings of the National Academy of Sciences.

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Geckos have millions of very small hairs on their toes. The end of each hair splits into as many as one-thousand smaller hairs. So the gecko's foot has hundreds of millions of tiny hairs that touch a surface.

Scientists have debated the purpose of these hairs. Some thought the hairs dug into a surface. Others thought geckos released a natural sticky substance onto their hairy toes to hold onto a surface, like a leaf, and prevent enemies from pulling them loose.

Over the years, scientists have put geckos into water to see if they would stick. They do. They have dropped them into strong devices, but their sticking ability was not weakened. Scientists also have used radiation to neutralize static electricity. They thought electrostatic force helped the animals hold on to a surface.

Scientists say the gecko's sticking power comes from something called the van der Waals force. The term was named after the Dutch scientist who first described it more than one-hundred years ago. The force is the attraction between molecules at the ends of the gecko's toe hairs and the surface of an object. When molecules are so close together, the unbalanced electrical charges around the molecules can attract one another. This provides the attraction between the foot of the gecko and a wall or other object.

The scientists showed that a single gecko toe hair has enough holding power to lift an insect. They say a small group of hairs the size of a coin could possibly lift a small child.

Scientists say they have created the first sticky substance based on the geckos' hairs. They hope to use the powerful substance to develop new products. The scientists recently joined with a company to develop robots that can climb walls.

This VOA Special English ENVIRONMENT REPORT was written by Cynthia Kirk.