Jadon Sancho is the youngest member of the England squad, with the Borussia Dortmund winger being just 18 years old. However, playing in the Bundesliga for the last year has meant that he was not a surprise selcetion. A man a year his senior was though.
Mason Mount is currently playing for Derby County, managed by former England midfielder Frank Lampard, and is on loan from Chelsea. He's never made a senior apperance for the 'Blues' and his only other senior experience is a year spent at Dutch outfit Vitesse Arhem.
In the Netherlands, Mount had an excellent season finishing with a tally of 14 goals and 10 assists, numbers that made those at his parent club Chelsea recognise that they had a serious talent on their hands.
The youngester was also part of the England U-19 that won the World Cup in 2017, where he was voted as player of the tournament such was the standard of his performances.
This season he has already scored five goals for Derby in the Championship and was part of the team that beat Man Utd at Old Trafford in the EFL Cup, scoring his penalty in the shootout.
His pick in the side shows the extent to which Southgate wants to back youthful players for the future, even if they aren't playing at the highest level possible.