Dortmund's young guns (from L) Felix Passlack, 18, and Christian Pulisic, 19, celebrate scoring a goal during their Champions League match against Legia Warszawa, in Dortmund, in November 2016
Youth will be showcased on Tuesday when the talent factories of Borussia Dortmund and Monaco square off in the Champions League quarter-finals.
Both clubs pride themselves on the business model of recruiting raw, young talent to nurture into superstars.
The first-leg quarter-final at Borussia's Signal Park Iduna sees Monaco, whose squad average 25.3 years, shade Dortmund, at 25.6 years, for the youngest of the last eight teams in Europe.
Both clubs are packed with rising stars.
Dortmund's Christian Pulisic, is a fully-fledged US international who turns 19 in September.
In April 2016, the attacking midfielder became the youngest foreigner to score in Bundesliga history.
His rise through the US youth national teams was mirrored at Dortmund where he was promoted to the first-team after just 15 academy games.
Monaco's forward Kylian Mbappe turns 19 in December and made his France debut last month.
He broke Thierry Henry's 21-year-old record in December 2015 when he became Monaco's youngest player, aged 16 years and 347 days, then broke another Henry record two months later by scoring his first goal.
Mbappe and Pulisic proved their worth in the Champions League last 16.
Mbappe gave his side the lead to help beat Manchester City 3-1 in their stunning second-leg win, as Monaco went through on away goals after a 6-6 draw on aggregate.
Likewise, Pulisic scored his first Champions League goal last month in the 4-0 second-leg win over Benfica.
His second-half strike opened the floodgates as Pierre-Emerick Aubameyang went on to score a hat-trick to progress 4-1 on aggregate.
Both Dortmund and Monaco are seeing their recruitment policy bear fruit.
Alongside Mbappe, Monaco have defender Djibril Sidibe, 24, defensive midfielder Tiemoue Bakayoko and winger Bernardo Silva, both just 22 -- and all four are internationals.
Likewise, Dortmund's winger Ousmane Dembele, 19, plays for France, Julian Weigl, 21, is a Germany international, Raphael Guerreiro, 23, won Euro 2016 with Portugal and Emre Mor is nicknamed "the Turkish Messi" by his home press.
Both club's philosophies were born of financial necessity.
Dortmund came back from the brink of bankruptcy in 2005, leaving CEO Hans-Joachim Watzke vowing never to spend heavily to buy in success.
Dortmund make their money from the stock exchange, having first been floated in 2000, but spend carefully.
On average, Dortmund spend 11.2 million euros ($10.5m) for a new player - a reasonable risk which leaves the door open to a huge increase if sold on.
"This is the only possible way for us," said Dortmund's director of sport Michael Zorc.
- Learnt lessons -
"Our turnover is about 200 million euros lower than the five or six biggest clubs in Europe and our payroll is around 100 million less."
Monaco are backed by Russian billionaire Dmitry Rybolovlev, who bought a 66.67 percent stake in December 2011.
However, UEFA's Financial Fair Play rules led to the club being sanctioned for splashing out for Porto pair Joao Moutinho and James Rodrigeuz, plus Atletico Madrid's Radamel Falcao, in 2013.
James was off-loaded to Real Madrid, Falcao went on loan to Manchester United, then Chelsea, and a policy change was implemented.
Sidibe joined from Lille in 2016, Bakayoko from Rennes in 2014, Silva was permanently signed in 2015 after a loan spell from Benfica, but each reportedly came for 15 million euros or less.
Yet all three are estimated to be worth at least double that.
As Monaco's vice-president Vadim Vasilyev puts it: "We are a selling club. But we do not have to sell if we do not want to."
Dortmund are already used to selling top players for double-digit sums.
Before this season, Manchester United swooped for Henrikh Mkhitaryan, Manchester City signed Ilkay Gundogan and Bayern Munich spent 35 million on buying back Mats Hummels having sold him for 4.2m euros in 2009.
Dortmund's goal-machine Aubameyang, who has scored 32 times in all competitions this season, could be next having hinted he may leave in June.
The Gabon striker has made no secret of his desire to one day play for Real Madrid.
Having paid Saint-Etienne 13 million euros for him in 2013, Dortmund can expect to make at least four times that.