Mbappe, Rashford & the 20 youngest players at World Cup 2018

Gudmundsson came through the academy at PSV and, after scoring 28 in 63 games for their reserve team, the winger has since been promoted to the senior side where he has made nine appearances so far.

The 20-year-old has also made an impressive start to his senior Iceland career, scoring three goals from his five caps so far. 

Amine Harit came through the academy at French side Nantes and he impressed enough to earn himself a move to German side Schalke, where he has made 29 league appearances during his debut season. 

After playing for France at youth level, Harit decided to change allegiances to represent Morocco and he has three caps so far after making his debut in October of last year. 

Bassem Srarfi made the move to Nice from Tunisian side Club Africain on deadline day of the 2017 January transfer window. 

The midfielder has gone onto make 37 appearances in all competitions for Nice so far and he made his Tunisia debut in March. 

Rodrigo Bentancur officially joined Juventus last summer from Boca Juniors after impressing for the Argentine outfit.

The midfielder has not been short of first-team opportunities during his first season, making 27 appearances in all competitions and he has also been capped six times by Uruguay after making his debut last September.

Dolberg is another example of Ajax's brilliant youth setup. Since breaking into the first team in 2016, the forward has scored 32 goals from his 77 appearances in all competitions.

He has so far been capped four times by Denmark and it is only a matter of time until one of Europe's elite snap up the talented youngster. 

After coming through the ranks and impressing with Partizan Belgrade, Nikola Milenkovic made the move to Serie A side Fiorentina last summer. 

The centre-back made 16 league appearances during his debut season and, since earning his first senior cap for Serbia in 2016, he has now featured three times for the national team.

Left-back Hamza Mendyl plays for French side Lille and he made his senior debut in February of last year. 

The 20-year-old has already been capped 13 times by Morocco after making his debut in an African Cup of Nations qualifier in April 2016.

Edson Alvarez plays for Mexican side Club América and, since making his debut in 2016, he has gone on to make 67 appearances in all competitions. 

The defender has also been capped 11 times by Mexico and he got his debut goal in the Gold Cup against Curaçao when he became the youngest Mexican player to ever score in the tournament. 

Rashford made the most of an injury stricken Manchester United strike force to break into the first team in 2016, scoring twice on his debut in the Europa League and then again on his Premier League bow against Arsenal a few days later.

The forward has gone onto make 123 appearances for United, scoring 32 goals, as he has become one of England's most exciting players. He made his case to start in the World Cup stronger by scoring a wonder goal against Costa Rica last week. 

Last summer Jovic signed on at Eintracht Frankfurt on a two-year-loan from Benfica. The youngster earned a move to Benfica in 2016 after scoring 13 in 48 games for Serbian side Red Star Belgrade. 

The striker played his part in scoring eight goals from his 22 league games during his debut season as Frankfurt finished eighth in the Bundesliga. 

Last summer Lee Seung-woo signed for Italian side Hellas Verona from Barcelona, but the Spanish giants have an option until 2019 to re-sign the winger.

The 20-year-old made 14 league appearances for Verona in his debut season as they were relegated to Serie B. 

The winger made the switch to Rennes in 2017 after breaking into the first team with league rivals FC Metz at the age of 18.

The Senegal international has made 24 league appearances during his debut season for Rennes and he has scored five goals. 

The right-back plays for Swedish side IFK Norrkoping, where he has made three appearances since signing for them earlier this year.

He came on as a late substitute for Costa Rica against England last week as his side were defeated 2-0. 

The midfielder made the move to Belgium side Gent at the end of December 2016 after initially joining on loan.

The 19-year-old has been playing for their U21 side all season and has been capped twice by the Panama senior team before being included in their World Cup squad. 

The right-back plies his trade for Belgium side Eupen and has made 28 appearances in all competitions this season. 

Claude Makelele is the coach of Wague's Eupen, and the former Chelsea midfielder masterminded their safety in the Belgium First Division this year with a 4-0 win on the final day of the league season.  

Alexander-Arnold has had a tremendous breakout campaign for Liverpool this season, making himself the first-choice right-back at Anfield.

He played a key role in Liverpool's run to the Champions League final and he is set to be an integral player for both club and country in the years to come.

The 19-year-old goalkeeper was promoted into Deportivo La Coruna's first team and played second fiddle to their No 1 Ruben Ivan Martínez.

Uzoho made his senior debut for Deportivo while he was 18 and becoming the youngest ever foreign goalkeeper to debut in La Liga. 

The Moroccan full-back broke through the ranks at Real Madrid's this season after making 28 appearances for their reserve team last year. 

The 19-year-old has become Dani Carvajal's back-up this season and has made nine league appearances, scoring his first La Liga goal against Sevilla in December. 

The France international rose to prominence breaking into the first team at Monaco at the age of 16 and he soon asserted himself as one of the most promising young players in world football.

His form earned him an initial loan move to Paris Saint-Germain last summer and he scored 21 goals in all competitions during his debut season and a permanent move to Parc des Princes will make him the second most expensive player ever behind team-mate Neymar.

The attacking midfielder is the only player born in the year 1999 to be playing at this year's World Cup.

Arzani, who made 20 appearances in all competitions for Melbourne City this season, has already been capped twice by Australia and scored his first senior goal last week against Hungary.