7 Years was released by Danish pop band Lukas Graham in 2015 as the lead single from their self-titled second album, written by frontman Lukas Forchhammer about ageing and looking back on life. The song became a worldwide hit, topping charts in several countries and earning billions of streams, which made its opening instantly recognisable. Years later it still circulates in short clips because that opening works as shorthand for nostalgia, letting creators signal childhood, time passing and growing up in just a few seconds.