For Letter X, my choice is X-Ray
Most of us have had an X-ray done for something or the other.
On November 8, 1895, physicist Wilhelm Conrad Röntgen becomes the first person to observe X-rays, a significant scientific advancement that would ultimately benefit a variety of fields, most of all medicine, by making the invisible visible.
Röntgen’s discovery was labeled a medical miracle and X-rays soon became an important diagnostic tool in medicine, allowing doctors to see inside the human body for the first time without surgery. In 1897, X-rays were first used on a military battlefield, during the Balkan War, to find bullets and broken bones inside patients. Though X-rays are very helpful in many diagnostic procedures, they carry the risk of skin damage, burns, and cancer.
Science has progressed a lot since those early days, and many new procedures are now in practice for diagnosis, but a simple X-ray is still the most simple and useful tool in diagnosing bone fractures, deformities, and other abnormalities. As a med student, I realize how vital this tool is even now.