Chelsea have confirmed the signing of teenage defender Kurt Zouma from Saint-Etienne.
Zouma joins the Blues on a five-and-a-half year deal, but will go straight back to the French club on loan for the rest of the campaign - and he may also go back there next season.
The fee is undisclosed but is reportedly in the region on £12million.
Zouma, 19, is a centre-back who has made 12 appearances in Ligue 1 this season, and 52 in total.
The 6'2" France Under-21 international came through the ranks at Saint-Etienne, whom he joined as a 15-year-old.
Chelsea manager Jose Mourinho said Zouma would be his last piece of business in the transfer window.
"Job done," Mourinho said. "The last one in the transfer window. In almost every position, we have the present and also the future.
"If we don't do it now, probably we can't do it in the summer because other clubs were also very strong on him.
"So we did it, now he stays at Saint-Etienne, pre-season he will join us. We will see if it is to stay or if it is to go on loan.
"He's another young player in the profile of some Chelsea signed in the couple of last years.
"We liked the profile, we think he's very much adapted to the Premier League. He is a young player for a position where we also need the future.
"He's a player with big potential, physically ready. One thing is to be physically ready, another thing is to be tactically ready. Well done Chelsea."