Each issue is devoted to a theme, such as water, air, or mirror.

When light travels through a material, such as glass, water, or even air, it moves more slowly.

It may be used to heat any kind of substance or material, such as oil, air, or sugar.

Here the fluid may be any material that contains thermal energy, such as water or air.

They are even absorbed quickly in gasses such as air.

Sound is made of waves that travel through a medium, such as air or water.

It is used in a variety of applications, such as food, air and water purification.

Animals move through a variety of fluids, such as water, air and mud.

The biggest challenge for our future is the decrease in natural resources such as clean air, pure water and a healthy environment.

If the objects are in a material such as air, other things play a part.