"My Songs Know What You Did in the Dark (Light Em Up)", also known as simply "Light Em Up", is a song by American rock band Fall Out Boy, released as the lead single for the band's fifth studio album, Save Rock and Roll. It serves as the band's first single following the group's three-year hiatus and regrouping in early 2013. The track and its music video were released on February 4, 2013, worldwide and February 5, 2013, in North America, to coincide with the official news of the band's reformation. The song impacted radio on February 19, 2013. The band members felt that the song best represented their album at its core.