Gamma rays are a type of electromagnetic radiation with the highest energy and shortest wavelength in the electromagnetic spectrum. They are produced by nuclear reactions, such as radioactive decay, nuclear fusion, and nuclear fission. Gamma rays have no mass or charge and can penetrate through most materials, including human tissue. They are highly ionizing and can cause damage to living cells, making them potentially harmful to humans and other organisms. However, gamma rays also have various beneficial applications, such as in medical imaging, cancer treatment, and sterilization processes.