A bikini is typically a women's two-piece swimsuit featuring two triangles of fabric on top, similar to a bra and covering 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 full coverage of the breasts, pelvis, and buttocks, to very skimpy designs like a thong or G-string that cover only the areolae and mons pubis but expose the buttocks.
In May 1946, fashion designer Jacques Heim from Paris released a two-piece swimsuit design that he named the Atome. 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 only four days before. His skimpy design was risque, exposing the wearer's navel and much of her buttocks. No runway model would wear it, so he hired a nude dancer from the Casino de Paris to model it at a review of swimsuit fashions.
Due to its controversial and revealing design, the bikini was accepted very slowly by the public. It gained increased exposure and acceptance as film stars like Brigitte Bardot, Raquel Welch, and Ursula Andress wore them and were photographed on public beaches and seen in the film. In many countries, the design was banned from beaches and other public places.
The minimalist bikini design became common in most Western countries by the mid-1960s as both swimwear and underwear. By the late 20th century it was widely used as sportswear in beach volleyball and bodybuilding. There are a number of modern stylistic variations of the design used for marketing purposes and as industry classifications, including monokini, microkini, tankini, trikini, pubikini, and skirtini. A man's single-piece brief swimsuit may also be called a bikini. Similarly, a variety of men's and women's underwear types are described as bikini underwear.
The bikini has gradually gained wide acceptance in Western society. By the early 2000s, bikinis had become a US$811 million business annually and boosted spin-off services such as bikini waxing and sun tanning.