May 8 was the last day of the MLS primary transfer window. There will be another one along shortly, allowing clubs to scoop up players from global soccer's annual summer transfer free-for-all, but for now teams in MLS can no longer sign players under contract in other countries (well, they can sign them, but they can't play in MLS until the transfer window opens again on July 10) or trade for players in the league already (again, they can do whatever deals they like in principle but no one moves until the window is open again).
Transfer deadline day is an exciting moment.