The first ever transfer operation was the one of Virginio Rosetta: in 1923 he was transferred from Pro Vercelli to Juventus for 45.000 lire
December 15, 1995: with the "Bosman ruling” the European Court of Justice gave professional players with EU citizenship the right to a free transfer at the end of the contract.
So far the most expensive transfer ever is the one of Welshman Gareth Bale: in 2013 he was transferred from Tottenham to Real Madrid for €109 million.
The most expensive defender of all time is Brazilian David Luiz: in 2014 he was transferred from Chelsea to Paris Saint Germain for €62.6 million.
The best gain in football transfer market is the one of Manchester United with Cristiano Ronaldo: he was bought for €17.5 million and sold for €94 million.
The worst loss is the one FC Barcelona: Swedish Zlatan Ibrahimovic was bought for €69.5 million and sold one year later for €24 million.
In 2001 Lazio bought Gaizka Mendieta for about €48 million: in one season he failed to score in 20 matches. The next year he was loaned to FC Barcelona.
Former German goalkeeper Lutz Pfannenstiel is the star of transfer market: in a 20-year career he was signed by 25 clubs and played in all 5 continents.