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 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.

Barcelona will look to knock the wind out of Inter's sails when the teams meet at the Estadi Olímpic Lluís Companys to kick off their UEFA Champions League semi-final. UEFA.com previews all the action ahead of the first leg on Wednesday 30 April. Kick-off time is 21:00 CET.