The last four teams standing return to play in the UEFA Champions League this week for the first leg of the semifinals, when some of Europe's top sides will begin to map out their route to the final on May 31 at Munich's Allianz Arena.

How does it work?Thirty-six sides entered into the new "league phase" and now just four remain with a month-and-a-half to go in the UCL campaign.Barcelona, Paris Saint-Germain, Arsenal, and Inter Milan are through to the semifinals,

The Champions League is down to four, with one club from four of Europe’s top five leagues represented in the semifinals. PSG the champions of France, takes on Arsenal in London, while Barcelona hosts Inter Milan during a chaotic time for both clubs.