Mbappe, Martial & the world's most expensive teenagers

Already labelled the 'next Messi', Pietro Pellegri is the joint-youngest player to line up in Serie A. Born in 2001, he became the most expensive 16-year-old ever despite having played just 10 senior games for Genoa.

Pellegri also scored twice against Lazio, setting the record as the youngest player to score two goals in a game in one of Europe's top five leagues.

When Manchester United tried to sign Anderson from Porto in 2007, they saw their work permit application turned down due to a lack of experience. United argued that at 19, it was impossible for him to have any more experience having helped Porto to back-to-back Primeira Liga titles.

The application was successful, but Anderson's time at Old Trafford was not as good as expected, despite playing over 100 Premier League games.

An Olympic champion with Brazil, Gabriel Jesus won everything possible domestically before leaving Palmeiras for Manchester City. The striker made an immediate impact in the Premier League, scoring and assisting in his first league start for Pep Guardiola's side.

Injury curtailed his debut season, but he still ended the campaign with seven goals and four assists in 11 appearances.

A sensation with Benfica in his native country, midfielder Renato Sanches was bought by Bayern Munich even before he won the Young Player of the Tournament award at Euro 2016.

Bayern had agreed to purchase him for €35m before the tournament, possibly saving themselves from a larger fee after his string of impressive performances as Portugal lifted the trophy.

England's youngest ever goalscorer joined Manchester United from Everton in 2004 as an 18-year-old, having already played 67 times in the Premier League.

At United, he went on to win every single trophy possible, including five Premier League titles, the Champions League in 2008 and then the Europa League in his final season at the club.

Having made his competitive debut with Southampton at just 16, England underage left-back Luke Shaw was one of the most desired young players in Europe.

With two full Premier League seasons under his belt for the Saints, Manchester United made him the world's most expensive teenager in 2014, beating off competition from Chelsea.

Now at Tottenham following a £25 million switch, Brazilian winger Lucas Moura arrived in Paris in the summer of 2012 following a tug-of-war between Manchester United, Inter and PSG.

At the time, he was PSG's record signing, and went on to play over 200 games for the club, winning four Ligue 1 titles.

Real Madrid paid the buyout clause in Vinicius Junior's Flamengo contract following the Brazilian's standout performance at the 2017 South American Under-17 Football Championship, where he picked up the award for the tournament's best player.

At the time of Madrid's offer, Vinicius had not even played a senior game of club football, but became one of their key players in the 2017 season as the Spanish side could not officially sign him until he turned 18. Vinicius will also spend 2018 and the first-half of 2019 back on loan in Brazil.

Anthony Martial became the world's most expensive teenager when he moved to Manchester United in September 2015. Two years earlier Monaco had spent just €5 million on him, taking a risk on the attacking midfielder despite just four senior games under his belt.

He flourished in his second season at Monaco, scoring 12 times in 48 appearances across all competitions, leading United to break the bank for his signature.

Having broken the world transfer record to sign Neymar for €222 million, PSG continued their summer 2017 acquisitions by signing the brightest young talent in world football. Mbappe arrived in Paris on an initial loan from Monaco, with the deal set to become permanent 12 months later for a fee that could rise as high as €180 million.

The French teenager netted 26 goals in all competitions in 2016-17 for Monaco, and has continued that dominance in front of goal in Paris.