The modern era of comics in Japan began after World War II, propelled by the success of the serialized comics of the prolific Osamu Tezuka and the comic strip Sazae-san. Genres and audiences diversified over the following decades. Stories are usually first serialized in magazines which are often hundreds of pages thick and may over a dozen stories; they are later compiled in tankōbon-format books. At the turn of the 20th and 21st centuries, nearly a quarter of all printed material in Japan was comics. translations became extremely popular in foreign markets—in some cases equaling or surpassing the sales of domestic comics.