Scientists discovered a hole in the ozone layer in 1980, and by 2000, the hole was three times the size of the United States. Through global efforts, scientists discovered the cause and worked together to get countries to implement a solution. Now the hole shrinks a bit every year and might one day be eliminated. A video from a larger series discusses the process of chemists finding the cause and how their attempts to solve a mystery about the atmosphere on Venus ended up offering ways to save the Earth's ozone layer.