The first American soap operas aired on television in the 1940s, but soaps achieved their first widespread popularity in the 1950s. The genre takes its name from the fact that early sponsors of the programs - including the manufacturers of cleaning products - took advantage of the predominantly female audience of the shows to pitch products that appealed to housewives.
Soap operas are not episodic - that is, their storylines don't begin and end within a single episode. Instead, multiple plot lines span many episodes, and the series usually feature large casts of many characters who interact in complex ways. Traditionally, the storylines of soaps revolve mostly around romance, family drama and personal relationships, but since the 1980s, soaps have increasingly incorporated medical and legal drama, adventure- and crime-related storylines and even supernatural elements.
For the first decade or more of their popularity, soaps were almost always part of the broadcast networks' daytime schedule, with original episodes of each series airing every weekday. In the 1960s, "Peyton Place" became the first popular night-time soap, and in the 1980s, the genre made a full-scale leap to the networks' primetime schedule with series such as "Dynasty" and "Dallas." Soon, too, the genre's format - ongoing storylines and large casts - was commonly used in non-soap TV drama series.
In the 1990s, the primetime soap became more youth-oriented, with series such as "Beverly Hills 90210" and "Melrose Place," and many popular series of the first decades of the 2000s, like "Grey's Anatomy" and "The Vampire Diaries," are essentially soaps.