Barcelona have completed the signing of full-back Hector Bellerin following an agreement with Arsenal to terminate his contract.
The 27-year-old joined the Gunners from Barca's youth ranks in 2011 and graduated from Arsenal's academy to become a regular in the first-team squad.
Named in the PFA Team of the Year in the 2015-16 season, Bellerin won the FA Cup three times with Arsenal, but ultimately fell out of favour under Mikel Arteta.
He joined Real Betis on loan last season, making 23 LaLiga appearances and helping Manuel Pellegrini's team win the Copa del Rey.
Betis were reportedly keen on signing Bellerin on a permanent basis but were unable to do so due to his wage demands, while Sassuolo were eager to bring him to Italy.
However, Barca have completed the move on a free transfer after Arsenal agreed to terminate his contract, which had one year left to run, having done similar to land Pierre-Emerick Aubameyang in January.
Bellerin adds to what has been a busy transfer period for Xavi at Barcelona, who have signed the likes of Robert Lewandowski, Jules Kounde and Raphinha, with Chelsea full-back Marcos Alonso also on the way.
Arteta told Arsenal's official website: "We say goodbye to Hector and we thank him so much for his loyalty and commitment to Arsenal Football Club. During his 11 years with Arsenal, Hector won three FA Cups and made nearly 250 appearances – such a huge contribution to the club.
"I'm privileged to have played in the same squad as Hector for three seasons, wearing the Arsenal shirt and sharing many great moments on and off the football pitch together. We thank you Hector and wish you and your family all the best for your return to Barcelona."