Mitochondria, also known as "mito" for short, are organelles found in the cells of most eukaryotes, such as animals, plants, and fungi. They have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used throughout the body as a source of energy. Mitochondrial disease is an umbrella term for a group of genetic disorders that affect how mitochondria function in the body. There are many different types of mito, with over 350 genetic causes identified so far. All types are considered rare, but some are more common than others. Symptoms of mito can be mild, such as tiredness or weakness, or they can be severe, such as poor growth, loss of muscle coordination, muscle weakness and pain, seizures, vision and/or hearing loss, gastrointestinal issues, learning disabilities, and organ failure. Approximately 1 in 4,000 people have mito. There is no cure for mito yet, but there are treatments that can help with the symptoms.