How do physicians and other health care providers explore the inside of the body?

Until the end of the 19th century, there were no noninvasive techniques to explore the internal organs of the body. Medical practitioners relied on descriptions of symptoms as the basis for their diagnoses. X-rays, discovered at the very end of the 19th century, provided the earliest technique to explore the internal organs and tissues of the body. During the 20th century, significant advances were made in the field of medical imaging to explore the internal organs.