Multum in Parvo

On Thanksgiving Day, 1931, there was discovered the first atom whose properties were predicted in advance by quantum theory. It was found by a combination of atomic spectroscopy and low temperature physics. At birth a minor satellite line in the Balmer spectrum of atomic hydrogen, it became a Nobel namesake at the age of three, and revolutionized chemistry; as a teenager it caused bloody fights in World War II; and coming of age, at 21 it fueled the first manmade thermonuclear chain reaction. Many of its side effects are seen in atomic, molecular and optical physics today.