Transfer fees in football have spiralled out of control in recent years.Back in 2017, Paris Saint-Germain obliterated the transfer record set by Manchester United and Paul Pogba by signing Neymar for £198m.Neymar's move more than doubled the £89m United spent on Pogba and in the 12 months that followed, the £100m barrier was broken three more times.Barcelona signed Ousmane Dembele from Borussia Dortmund for £135.5m and Philippe Coutinho from Liverpool for £142m, while PSG added Kylian Mbappe to their ranks for £165m.It won't be long before the first £200m transfer, which is incredible when you consider that the transfer record 20 years ago in 1999 was £32.5m for Christian Vieri.Three years before that, Barcelona spent £13.2m to sign Ronaldo Nazario from PSV Eindhoven to break the record. He then joined Inter Milan the following year for £19.5m.Transfer fees are only going to keep rising and it's a wonder who the next world-record signing will be. Neymar, for example, is being linked with a £300m move to Real Madrid this summer.It's also likely that Mbappe, 20, will be involved in another big-money move at some point in his career, so who knows how much he will cost in the future.Football is evolving and a fascinating live graphic has emerged showing the evolution of the most expensive transfers since 1990.In the video below - which uses euros as its currency - Diego Maradona starts off as the most expensive transfer before being overtaken by Gianluca Vialli. It just snowballs from there.

Crazy. European clubs are richer than ever before so it's no surprise that they're spending more money to sign their top targets.

Fast forward to 2020 and there's a good chance the graph will need to be extended beyond the £200m mark.