Electricity is required for proper function of an animal's body. Biological cells use it in many ways, such as in the heart, eyes, and nervous systems. Some animals have special organs that produce electricity. For instance, electric eels and sharks use electricity to catch prey, while others use it to defend themselves or navigate. The field of research involving electricity in the body is sometimes called Bioelectrics, and it is still an active area of research today. Medical professionals also use electricity to affect our bodies, such as for defibrillation and electrolysis.