Louis Slotin was born on December 1, 1910 in Winnipeg, Manitoba, Canada. He was the eldest of three children in a family of Jewish refugees from Russia. From an early age he demonstrated great potential in science and mathematics.

At the age of sixteen, he enrolled at the University of Manitoba, pursuing a degree in science. During his studies he received a University Gold Medal in physics and chemistry, graduating with a Bachelor of Science degree in geology in 1932. In 1933 he earned his Master of Science degree, after which he moved to King's College in London to study under Arthur John Allmand.

In 1936, he received a doctorate in physical chemistry from King's College. His thesis, "An Investigation into the Intermediate Formation of Unstable Molecules During some Chemical Reactions", also won him a prize. For the next six months, he worked for Dublin's Great Southern Railways, testing nickel-zinc batteries.

In 1937, he moved to Chicago to work as a research associate at the University of Chicago. There, he started working on nuclear chemistry projects and helped to build a cyclotron. Using the cyclotron, he and a colleague, Earl Evans, were able to produce radiocarbon. While working with radiocarbon, they discovered that animal cells had the capacity to use carbon dioxide during carbohydrate synthesis. Over the next several years he continued researching nuclear biology and physics.

Eventually, his work caught the eye of the United States government, which was working to put together the Manhattan Project. His first tasks involved producing plutonium at the university with Eugene Wigner, later moving to Oak Ridge National Laboratory. In December of 1944, he moved to Los Alamos National Laboratory to work in Robert Bacher's bomb physics group.

At Los Alamos, Slotin was tasked with performing dangerous criticality testing, which involved bringing masses of fissile materials to near-critical levels to find out their critical mass values. This dangerous experimentation with nuclear fission was nicknamed "Tickling the Dragon's Tail" by the scientists. His first criticality tests uses uranium, followed by plutonium. On July 16, 1945 he assembled the core for Trinity, which was the first atomic bomb to be detonated in history.

On August 21, 1945, Slotin's colleague and lab assistant, Harry Daghlian, was performing a critical mass experiment when the mass of tungsten carbide fell onto the plutonium core and irradiated him with 510 rems. Slotin spent much of his time at his bedside over the next twenty-one days as he slowly died from the radiation. Unbeknownst to Slotin, he would suffer the same fate not long after.

On May 21, 1946, Slotin was working with seven colleagues on an experiment that created the first steps of nuclear fission by placing two half-spheres of beryllium around a plutonium mass. The scientists normally used shims to separate the masses, but Slotin decided to use a screwdriver blade instead. That decision would be his undoing, as the screwdriver slipped at about 3:20 PM.

The beryllium mass on top of the plutonium fell onto it, causing a fission reaction that released incredible amounts of radiation. Other scientists in the room observed a blue glow of ionized air and also felt a heat wave. Slotin described a sour taste in his mouth and burning feeling in his hand, which was on the top beryllium half-sphere. He quickly jerked his hand back, dropping the half-sphere on the floor and ending the reaction.

It was determined that he had exposed himself to about 2100 rems of neutron and gamma radiation, equivalent to what he would have received standing 4800 feet from an atomic bomb explosion. As soon as he left the building he vomited and his colleagues rushed him to the hospital. He soon developed symptoms of severe diarrhea, swollen hands, massive blisters, decreased kidney and bowel function, and gangrene. He died after nine days of extreme pain, on May 30, 1946. The incident was later portrayed in the 1989 film, "Fat Man and Little Boy", with John Cusack playing a character based on Slotin.