X-rays are high energy waves that are invisible. They are useful because they can pass through many things that normal light cannot. For example, doctors can see inside the human body and security guards at airports can see inside your handbag.
Asthma occurs when tissue in your throat begins to expand or swell. Muscles in these passages become tighter and cells begin to produce some sticky substance, which makes airways even smaller.
Studies have shown that about 30% of all children in America aged 6 to 19 are either overweight or obese. That is almost one out of three young Americans. The situation in the countries of the European Union is similar.
Vaccines are substances that help the body fight off diseases and illnesses. In the past, they have helped save millions of lives around the world.
Cancer is a dangerous disease in which certain cells in our body grow in an uncontrolled way. It is one of the world’s most serious illnesses. Together with heart attacks, it kills more people than any other disease in the world.