RB Leipzig: The unusual story of Champions League semi-finalists

Just ten years ago RB Leipzig were making their debut in the fifth division of German football.

On Tuesday night, they play French champions Paris St Germain for a place in the Champions League final.

It's been a remarkable rise for one of the most controversial clubs in German football.

Here's what you need to know.

Rich owners, like you see in the Premier League, are generally frowned upon in German football, with fans traditionally having a big stake stake in the goings on at their club.

For example, Borussia Dortmund has 139,000 paying members who all have a say over things like season ticket prices.

But in 2006, Energy drink billionaire Dietrich Mateschitz wanted to buy a football club in Germany.

This was really controversial because critics believed he was only doing it to promote his energy drink, Red Bull.

After trying unsuccessfully to buy top flight German sides, he decided to go all the way to the bottom.

He bought a fifth-division club called SSV Markranstädt and rebranded them as RB Leipzig.

He wasn't allowed to include Red Bull in the title of the club so he chose Rasenballsport Leipzig, meaning "lawn ball sports".

It didn't take Leipzig long to shoot up the leagues with Mateschitz's money to spend and they were promoted into the German top league - the Bundesliga - in 2016.

It was the first time in 22 years that the city of Leipzig had a team in the top division.

Since that point, Leipzig have been known by opposition fans as 'the most hated club in Germany' and have faced regular protests.

It's the wide belief among German football fans that the club haven't climbed up the leagues in a proper and fair manner.

Borussia Dortmund chief executive Hans-Joachim Watzke has described RB "a club built to push up the revenues for Red Bull."

Despite claims that RB Leipzig have bought their way to the top of the football pyramid, they've not massive spenders.

Instead, they've focused their efforts on finding good young players and then building them into superstars.

In 2016, Leipzig bought Naby Keita from fellow Red Bull investment side, RB Salzburg, in Austria for £26 million.

Just two years later they sold him to Liverpool for £54 million.

It's the same story with Timo Werner, who was bought for £12 million and was then sold to Chelsea this summer for £47 million.

A young club needs a young exciting manager and Julien Nagelsmann is exactly that.

He started his management career at 1899 Hoffenheim as a 28-year-old, becoming the youngest manager in Bundesliga history.

The 33-year-old moved to RB Leipzig last summer and helped the club to third place in the league and to the Champions League semi-finals this season.

A highlight of the Champions League campaign was RB's 4-0 victory over last season's finalists Tottenham Hotspur over two legs.

The last time anyone beat German champions Bayern Munich to the league title, RB Leipzig were in the fourth division.

Leipzig have been in and around the top of places of the Bundesliga for a few years now but will hope they can challenge Bayern next season.

However, keeping hold of their best players will be the priority, with star striker Timo Werner - who scored 33 goals last season - having already been sold..

A replacement has already been found with Hee-chan Hwang.

Emerging defender Dayot Upamecano is another player Leipzig will be desperate to keep hold but he's attracting interest from some of the biggest clubs in Europe.

So you may not know much about RB Leipzig yet, but you better get used to hearing a lot more about them in the near future!