This has been confirmed by Chelsea via their website, though the exact details of the trade have yet to be released. It has been rumoured from Sky Germany (re-reported by both outlets above) that the initial fee is £8m with Romelu Lukaku heading to Werder Bremen on a season loan, but this hasn't yet been confirmed by Chelsea.
Twenty-three-year-old Marin has been dubbed as the German "Messi" due to his blistering speed and gifted technical ability. He will no doubt be deployed along the wing, injecting some much needed pace and youth to the Chelsea side next season.
Marin will join Kevin De Bruyne at the end of the season. His arrival along with other promising youngsters from last summer's transfer window, including goalkeeper Courtois and midfielders Paizon, Romeu and Mata, surely spells a new era for the Blues.
These promising signings create a sense of deja vu for Chelsea supporters who witnessed similar transfers when Abramovich first took over the club. If these youngsters mature in a similar manner, then there'll be plenty of good times ahead for the Chelsea Football Club.