A bikini is a women's two-piece swimsuit featuring two triangles of fabric on top that cover the woman's breasts, and two triangles of fabric on the bottom: the front covering the pelvis but exposing the navel, and the back covering the buttocks. The size of the top and bottom can vary, from bikinis that offer full coverage of the breasts, pelvis, and buttocks, to more revealing designs with a thong or G-string bottom that covers only the mons pubis, but exposes the buttocks, and a top that covers little more than the areolae.
In May 1946, Parisian fashion designer Jacques Heim released a two-piece swimsuit design that he named the Atome and advertised as "the smallest swimsuit in the world". Like swimsuits of the era, it covered the wearer's navel, and it failed to attract much attention. Clothing designer Louis Réard introduced his new, smaller design in July. He named the swimsuit after the Bikini Atoll, where the first public test of a nuclear bomb had taken place four days before. His skimpy design was risqué, exposing the wearer's navel and much of her buttocks.