El Shaaraway was finalising the switch yesterday.
"He has the Rossoneri in his heart and from today also on his shirt," said agent Roberto La Florio.
"Adriano Galliani never lets talents like this slip away! Milan wanted him more than anyone else and I can guarantee the deal would have been done even if Merkel didn't accept a move to Genoa.
"The only thing that Merkel changes is the financial cost of the operation. Milan have taken the 'Little Pharaoh' in a co-ownership deal and he will immediately join the club without any further loans.
"Milan and Genoa will meet on Saturday afternoon and everything will be made official then. This season half of Europe came to view him at Padova, as all the top clubs sent scouts, but Milan moved quicker than anybody."