Second Toughest in the Infants is the fourth studio album by British electronic music group Underworld, and the second in their "MK2" line-up with Darren Emerson. With this album, Underworld expanded on their progressive palette, while developing their signature sound of abrasive beats and anthemic melodies. The name of the album derives from a comment made by member Rick Smith's six-year-old nephew, Simon Prosser, when asked on his progress at infant school. Second Toughest featured the single "Pearl's Girl". The re-issue featured the band's best known single, "Born Slippy .NUXX".