An atom is the smallest component of an element that still retains the properties of the element.

Capillaries are small thin-walled vessels that permit the exchange of oxygen, carbon dioxide, nutrients, and waste between blood and the body's cells. This process of exchange is called diffusion.

Cumulus clouds are large, puffy, mid-altitude clouds with a flat base and a rounded top. These clouds grow upward and can develop into a cumulonimbus or thunderstorm cloud.

The water then accumulates as runoff and eventually returns to bodies of water or is absorbed into the Earth (infiltration) and becomes part of the water table, an underground resevoir of fresh water.

Because different materials have different refractive indices, light changes speed when passing from one material to another. This causes the light to bend (refraction) at an angle that depends on the change in refractive index between the materials. The greater the difference, the higher the angle of refraction.