Which team has the best academy in world football?
It's a question that has no right answer, especially given that the success of a club's academy can change dramatically from decade to decade.
However, there are those big-name teams that will always be in contention to have their academy labelled as the very best by a hefty percentage of fans.
One of those teams is Manchester United. Despite the club's decline in the post-Sir Alex Ferguson era, the Red Devils' youth setup still produces a lot of talented players.
In fact, United currently have 24 active players that were trained at the club across Europe's top five leagues.
That puts them ninth in the CIES Football Obseravtory's rankings, the highest position of any Premier League team.
So which team takes the number one spot? Well, let's find out...
*In accordance with the UEFA definition, training clubs are those where players have been for at least three seasons between 15 and 21 years of age.*
The 30 teams with the most academy players active in Europe's top five leagues
30. River Plate
Active players: 15
29. FC Nantes
Active players: 15
28. Southampton
Active players: 15
27. AS Roma
Active players: 15
26. Benfica
Active players: 15
25. Manchester City
Active players: 16
24. Osasuna
Active players: 17
23. AC Milan
Active players: 18
22. Bordeaux
Active players: 19
21. Stuttgart
Active players: 19
20. Sevilla
Active players: 19
19. Sporting Lisbon
Active players: 19
18. Celta Vigo
Active players: 20
17. Atalanta
Active players: 20
16. RC Lens
Active players: 20
15. Ajax
Active players: 20
14. Chelsea
Active players: 20
13. Atletico Madrid
Active players: 21
12. AS Monaco
Active players: 22
11. Saint Etienne
Active players: 22
10. Arsenal
Active players: 23
Active players: 24
8. Rennes
Active players: 25
7. Athletic Bilbao
Active players: 25
6. Real Sociedad
Active players: 26
5. Valencia
Active players: 28
4. Paris Saint-Germain
Active players: 29
3. Lyon
Active players: 31
2. Barcelona
Active players: 32
1. Real Madrid
Active players: 43
Real Madrid take top spot by quite some distance, with 11 players more than bitter rivals Barcelona in second place.
Bayern Munich (14 players), Tottenham (13 players), Juventus (12 players), Liverpool (11 players) and Borussia Dortmund (11 players) are the notable absentees from the top 30.
United, Arsenal, Chelsea, Manchester City and Southampton are the five members of Premier League to feature, while La Liga is the most represented league with nine teams.