The January transfer window is now closed for the season and the Blues have made significant investments for the future.
In this month Nemanja Matic was signed from from Benfica.
On signing his five-and-a-half-year contract, the 25-year-old said: 'I am very happy for this opportunity to be back at this club. I feel very good because of that and just want to say I will give my best to help the team and make the Chelsea fans happy.'
Then it's Bertrand Traore (Association Jeunes Espoirs De Bobo-Dioulasso, free transfer).
Mohamed Salah joined Chelsea from Swiss side FC Basel on 26 January 2014. The Egyptian international penned a five-and-a-half year contract having passed a medical and obtained a work permit. He took the number 15 shirt.
Today Kurt Zouma was signed from St. Etienne. He will remain on loan at the French club for the rest of the season.
The 19-year-old central defender has joined Chelsea on a five-and-a-half year contract. This season he has made 12 league appearances for France's fourth-placed side.
The 6ft 2in Zouma is a French Under-21 international. He was born in Lyon and joined St. Etienne as a 15-year-old in 2009, turning professional in 2011. In total he has made 52 league appearances for 'Les Verts' and scored four goals.
Out this month went Juan Mata for £37.1m to Manchester United.
Gael Kakuta who completed a loan move to Lazio until the end of the season.
The French winger or attacking midfielder, who spent the past season and a half on loan at Vitesse Arnhem, moved to Chelsea from Lens in 2007 and has made 16 appearances for our first team. He made his debut as a substitute against Wolverhampton Wanderers in 2009 and has also represented the Blues in the Champions League.
So in conclusion, the ins and out are summarised aside as follows:
Ins: Nemanja Matic (Benfica, £20.75million), Mohamed Salah (Basle, undisclosed), Bertrand Traore (Association Jeunes Espoirs De Bobo-Dioulasso, free transfer), Kurt Zouma (St Etienne, undisclosed)
Outs: Juan Mata (Manchester United, £37.1million), Michael Essien (AC Milan, undisclosed), Bertrand Traore (Vitesse Arnhem, loan), Kenneth Omeruo (Middlesbrough, loan), Nathaniel Chalobah (Middlesbrough, loan), Patrick Bamford (Derby, loan), Kevin de Bruyne (Wolfsburg, £17million), Josh McEachran (Wigan, loan), Ryan Bertrand (Aston Villa, loan), Sam Walker (Colchester, free transfer)
Thanks to Chelsea FC and London24