U-M used transfer portal to win. What is the portal? When is it open?

The University of Michigan, which won the NCAA Men's Basketball Tournament this week, built its roster with transfer portal players — starting five players who began their collegiate careers at other schools. In fact, all of this year's men's Final Four teams relied heavily on players who transferred from other schools. The transfer portal opened at midnight after Michigan's 69-63 national championship win over UConn on Monday, April 6.

More than 1,500 players have already entered, according to multiple reports. Athletes announcing they will enter the transfer portal have the opportunity to switch schools. Created by the NCAA in 2018, the transfer portal has become a key pillar of college sports: A resource for student-athletes who hope for a different future, a program-building tool for coaches and a source of intrigue for fans.

Here's a look at how the portal works. What is the transfer portal? The transfer portal is a "compliance tool to systematically manage the transfer process from start to finish," The NCAA said .

The NCAA created the database in an attempt to simplify the first step in the transfer process. In the pre-portal days, athletes would have to ask their coach for permission to contact other schools, then find ways to get the word out that they were available. Coaches, meanwhile, would have to use their connections and word-of-mouth referrals to identify transferring athletes.