Screamo is an aggressive subgenre of emo that emerged in the early 1990s and emphasizes "willfully experimental dissonance and dynamics". San Diego-based bands Heroin and Antioch Arrow pioneered the genre in the early 1990s, and it was developed in the late 1990s mainly by bands from the East Coast of the United States such as Pg. 99, Orchid, Saetia, and I Hate Myself. Screamo is strongly influenced by hardcore punk and characterized by the use of screamed vocals. Lyrical themes usually include emotional pain, death, romance, and human rights. The term "screamo" has frequently been mistaken as referring to any music with screaming.

Emo is a music genre characterized by emotional, often confessional lyrics. It emerged as a style of hardcore punk and post-hardcore from the mid-1980s Washington, D.C. hardcore scene, where it was known as emotional hardcore or emocore. The bands Rites of Spring and Embrace, among others, pioneered the genre. In the early-to-mid 1990s, emo was adopted and reinvented by alternative rock, indie rock, punk rock, and pop-punk bands, including Sunny Day Real Estate, Jawbreaker, Cap'n Jazz, and Jimmy Eat World. By the mid-1990s, Braid, the Promise Ring, and the Get Up Kids emerged from Midwest emo, and several independent record labels began to specialize in the genre. Meanwhile, screamo, a more aggressive style of emo using screamed vocals, also emerged, pioneered by the San Diego bands Heroin and Antioch Arrow. Screamo achieved mainstream success in the 2000s with bands like Hawthorne Heights, Silverstein, Story of the Year, Thursday, the Used, and Underoath.