By the baby experts at Mayo Clinic. Mayo Clinic is the first and largest integrated, not-for-profit group practice in the world. Doctors from every medical specialty work together to care for patients, joined by common systems and a philosophy that the needs of the patient come first. Over 3,600 physicians and scientists and 50,000 allied staff work at Mayo, which has sites in Rochester, Minn. Jacksonville, Fla. and Scottsdale/Phoenix, Ariz. Collectively, Mayo Clinic treats more than 500,000 patients a year. For more than 100 years, millions of people from all walks of life have found answers at Mayo Clinic. Mayo Clinic works with many insurance companies, does not require a physician referral in most cases and is an in-network provider for millions of people.