A country explores nuclear weapons when it commissions studies to investigate the cost and plausibility of a nuclear weapons program without having begun active pursuit of the bomb. Fourteen countries have engaged in nuclear exploration before quitting: Nazi Germany, Japan, Switzerland, Sweden, Norway, Egypt, Italy, West Germany, Australia, Indonesia, Taiwan, Romania, Argentina, and Algeria. This lecture provides an overview of why those countries began exploration and what caused them to go no further. Photo of Japan's nuclear power plant is courtesy the IAEA imagebank (https://www.flickr.com/photos/iaea_imagebank/8388174199) and is licensed under CC 2.0: https://creativecommons.org/licenses/by-sa/2.0/ The IAEA/Brazil/Argentina photo is also licensed under CC 2.0.