Billie Eilish's debut studio album, "When We All Fall Asleep, Where Do We Go?", was released on March 29, 2019. The album was written largely by Billie and her brother Finneas O'Connell, who also produced it in his bedroom studio in Los Angeles. The album explores themes such as youth, heartbreak, drug addiction, suicide, and mental health, with inspirations drawn partly from Billie's experiences with lucid dreaming and night terrors. Musically, it features a mix of pop, electropop, avant-pop, art pop, with influences from hip hop and industrial music. The album was notable for its dark, surreal, and sometimes humorous tone. It became an immediate commercial success, featuring hit singles like "Bad Guy" and "When the Party's Over" and making Billie Eilish the youngest female solo artist to have a number one album in the UK. The title of the album itself comes from a line in the song "Bury a Friend," and the whole project reflects the surreal and sometimes terrifying nature of dreams and sleep experiences that Billie has described.