Professional football is a hard sport to break into and many of those who are trained at some of the best academies in the world still don't make it at the top level.
Research from the Football Observatory has now revealed exactly which youth setups are the most prolific in producing players - based on the criteria of an individual having spent at least three years at a club between the ages of 16 and 21.
Overall, it is perhaps unsurprising to learn that Ajax lead the way, with an incredible 77 of their academy graduates currently playing top flight football in various European leagues. Partizan Belgrade are second with 74.
In terms of clubs from Europe's Big 5 leagues (England, Spain, Germany, Italy, France), Atletico Madrid (24) and Manchester City and Inter Milan (both 23) narrowly missed out on making the top 16.
Here's a look at those who do feature.
11. Athletic Bilbao & 4 Others (26 players)
Given their rules on using only players from the Basque region, producing young talent forms a huge part of Athletic Bilbao's ethos and the current squad is filled with home-grown stars.
In total, 26 individuals schooled at San Mames are professionals throughout Europe's top divisions at the moment. The same number have also successfully come through the ranks at Montpellier, Metz, Real Sociedad and Valencia.
10. Rennes & Stuttgart (27)
Rennes and Stuttgart have each gifted top divisions across Europe 27 current professionals in recent years. Yoann Gourcuff and Yann M'Vila are two of the biggest names to have emerged from the French club's academy since 2003.
Stuttgart's current captain, Christian Gentner, came through the ranks at German club, as did journeyman striker Kevin Kuranyi, who is now playing his football for Dynamo Moscow.
9. Lens (28)
Lens were crowned champions of France in 2001/02, but have enjoyed something of a troubled existence in more recent years, returning to Ligue 1 this season. The club will be relegated straight back to Ligue 2 regardless of their finish, though, as a result of a court order that ruled the promotion invalid.
Despite the difficulties, the club's academy can still boast having 28 players at top flight clubs throughout Europe, including Real Madrid star Raphael Varane and rising Monaco midfielder Geoffrey Kondogbia
8. Monaco (30)
Monaco can count 30 of its academy alumni at clubs across Europe's top divisions, including French international goalkeeper Stephane Ruffier and Nice midfielder Nampalas Mendy, dubbed the 'new Makelele'.
Promising full-back Layvin Kurzawa is one of several current Monaco players to have been promoted from within, as is the team's vice-captain Valere Germain and Belgian midfielder Yannick Ferreira Carrasco.
7. Bayern Munich (32)
Bayern Munich have long enjoyed a tradition in producing many of Germany's great players going back to the days of Franz Beckenbauer and Sepp Mair in the late 1950s.
Across Europe today, there are 32 Bayern graduates in top flight clubs, the biggest of whom are still in Bavaria. Bastian Schweinsteiger, Philipp Lahm and Thomas Muller all came through the youth setup, as did Toni Kroos, who left for Real Madrid in the summer.
6. Arsenal (33)
Arsene Wenger has often been criticised for producing little to no English talent during his time at Arsenal, but 33 of the Gunners' former youth players, both local and foreign, are currently plying their trade throughout Europe.
Under the criteria, the Gunners can lay claim to Cesc Fabregas, with the Spaniard having joined the club when he was just 16, as well as Theo Walcott, Aaron Ramsey and even Manchester City full-back Gael Clichy.
5. Paris Saint-Germain (35)
Paris Saint-Germain's squad has been filled with a number of expensive imports since the club was bought by a Qatar-based investment fund, but the youth academy has been churning out talent since before and after the 2012 takeover.
There are a total of 35 PSG schooled players in top divisions across Europe at this very moment. Adrien Rabiot is the biggest home-grown talent in the current squad, while 27-year-old midfielder Clement Chantome recently left for Bordeaux.
4. Manchester United (39)
In recent memory, Manchester United have produced some of the best players that English football has ever seen with the famed Class of '92. Ryan Giggs was the last of that generation to hang up his boots, but there are still 39 former academy starlets playing in top flight leagues.
The current first team squad at Old Trafford is awash with a new generation of home-grown players, while there are also United graduates at various Premier League clubs, including Danny Welbeck, Ryan Shawcross, Tom Cleverley, Darren Fletcher, John O'Shea and Wes Brown.
3. Lyon (40)
Lyon are enjoying a real resurgence in France this season, having previously dropped away since their stunning run of seven consecutive national titles between 2002 and 2009.
During that time, the club had real pull in the picking of the top talent in France and now a total of 40 former Lyon graduates are plying their trade in top flight leagues - perhaps most notably Karim Benzema at Real Madrid. Alexandre Lacazette is a product of the youth system too and is lighting up Ligue 1 this season.
2. Real Madrid (47)
Real Madrid have a reputation for favouring the Galacticos brand over all else, but their youth academy is one of the most productive in all of Europe, with one or two even making a name for themselves in the club's first-team.
There are 47 Bernabeu trained players in Europe's top leagues at this moment in time. Iker Casillas has never left, while Dani Carvajal has made a big impact since breaking into the senior squad in 2013. Other famous graduates playing elsewhere include Juan Mata, Alvaro Morata and even Samuel Eto'o.
1. Barcelona (57)
Barcelona's dominance under the management of Pep Guardiola was built on the club's own talent, developed in the famed La Masia academy. In 2011, 10 of the 18 players selected for the Champions League final were home-grown and that doesn't even include Gerard Pique who spent his later teenage years at Manchester United.
Today there are 57 Barça graduates playing top flight football all over Europe. The most famous - Lionel Messi, Xavi and Andres Iniesta - are all still at Camp Nou. A whole host of the current squad are home-grown and there are many more elsewhere too, like Thiago Alcantara, Bojan Krkic and Marc Muniesa to name just three.