France, Germany, Romania and Spain are this year's semi-finalists. UEFA.com runs through the basics.
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Previous U21 best: winners (1988)
Coach: Sylvain Ripoll
Most recent starting XI: Bernardoni; Amian, Konaté, Upamecano, Sarr; Ntcham, Tousart, Guendouzi, Thuram; Mateta, Ikoné
Did you know? France finished 12 points clear at the top of their qualifying group, a bigger cushion than any other nation.
"When the coach took charge, he tried to understand why we hadn't qualified for so many years. He also tried to look into what we could improve. I think we could say he started from scratch, with a new generation and new players. He created a good atmosphere within the squad; we all feel good."
Lucas Tousart, France captain
Previous U21 best: winners x2 (2009, 2017)
Coach: Stefan Kuntz
Most recent starting XI: Nübel; Klostermann, Tah, Baumgartl, Henrichs; M. Eggestein, Dahoud; Öztunali, Neuhaus, Richter; Waldschmidt
Did you know? Kuntz was a member of Germany's EURO '96-winning side, scoring the equaliser against hosts England in the semi-finals and converting his penalty in the subsequent shoot-out. Kuntz's U21s also beat England on penalties in the last four of the 2017 tournament en route to lifting the trophy.
"We have a group of lads who will be playing their final games with us and I hope that we have a successful conclusion to their two years here."
Stefan Kuntz, Germany coach
Previous U21 best: quarter-finals (1998)
Coach: Mirel Rădoi
Most recent starting XI: Radu; Manea, Nedelcearu, Rus, Boboc; Nedelcu, Cicâldău; Olaru, Hagi, Coman; Puşcaş
Did you know? Romania had the joint best defensive record during qualifying with just four goals conceded in ten matches.
"Our team game is very good and, as I've always said, we are a force to be reckoned with in attack. We have very fast players with good technique."
Ianis Hagi, Romania midfielder
Previous U21 best: winners x4 (1986, 1998, 2011, 2013)
Coach: Luis de la Fuente
Most recent starting XI: Sivera; Aguirregabiria, Unai Nuñez, Jorge Meré, Aarón Martín; Fabián Ruiz, Marc Roca; Dani Olmo, Ceballos, Fornals; Oyarzabal
Did you know? Spain have reached three of the last four U21 EURO finals, losing to Germany in the 2017 decider having lifted the trophy in 2011 and 2013. They failed to qualify in 2015.
"I've always said that the Spanish U21 team is very important. Plus, with the Olympics on the horizon, it is even more important. We know it's the last stepping stone to the senior team."
Jesús Vallejo, Spain captain