It is an essential part of modern football. Before a new signing takes questions from the media or even - in some cases - meets his team-mates, he must pose holding his new club's shirt, displaying the number he has chosen to wear on his back to the world.
Inspired by deadline day, bundesliga.com went digging through the archives to find out the history of shirt numbers in Germany's top flight, discovering that it has not always been as prominent a presence as it may nowadays seem.
Shirt numbers have been used in Germany since 1948, but it was not until the August 1995 when players first stepped onto a Bundesliga pitch with fixed squad numbers on the backs of their shirts instead instead of the traditional 1 to 11. Fortuna Düsseldorf's Richard Cyron scored the first goal of that 1995/96 season, and the PA announcer at SV Werder Bremen's Weser Stadium – where Fortuna were playing their first game of the season – rubbed his eyes in wonder.
Watch: Enjoy an exclusive tour of the Bremen's Weser Stadium:
"The goalscorer, wearing the number 26 shirt," he cried into his microphone. Hardly a novelty today, but a moment when it is fair to say that German football changed forever.
There have been plenty of other changes in football in the intervening 21 years, over which time the shirt number has become something of a trademark for many players. Michael Ballack, for example, raised eyebrows upon his arrival at Chelsea FC when he demanded his favoured number 13 – then worn by William Gallas.