X-rays have wavelengths ranging from 0.001 nm to 60 nm and can penetrate many types of materials, including your body. Gamma rays have wavelengths shorter than 0.1 nm but the highest frequency of all electromagnetic waves. Gamma rays can easily pass through most materials. Fortunately, the Earth’s atmosphere blocks out most of this type of electromagnetic radiation coming from outer space. Doctors use both of these electromagnetic waves in small amounts as either an x ray to look inside the human body, or as gamma rays to kill cancer cells. Astronomers use satellites in outer space to collect x ray and gamma ray information to study the universe.