March Madness is underway. How to watch and what to look out for

March Madness has begun! On the tournament's opening day, only four out of 32 teams lost to lower-seeded foes but two of them were big: No. 2 seed Arizona and No. 4 seed Virginia both went down, busting millions of brackets.

Here is what to know going into Day 2 of the NCAA Tournament, including the favorites and underdogs as well as key games:

How to watch

Every game of the men's tournament will be aired — here is a schedule — either on CBS, TBS, TNT or TruTV and their digital platforms. CBS, which also has a handy schedule that includes announcing teams, will handle the Final Four and national title game this year.

The NCAA will again stream games via its March Madness Live option and CBS games will be streamed on Paramount+. Fans of longtime play-by-play announcer Jim Nantz should soak up every moment: It's his final NCAA Tournament.

Top seeds

The top four seeds in the tournament are Alabama, Houston, Kansas, and Purdue. Each is in a region, some tougher than others (on paper), and each has had its share of headaches to set up what could be a chaotic tournament. Here is the latest from each region:

East region

The Boilermakers got a No. 1 seed for the fourth time, but Purdue could face potential hurdles in Memphis and surging Duke. Savvy veteran coach Tom Izzo and Michigan State are in the East, too, facing a first-round matchup with Southern Cal and coach Andy Enfield of Dunk City fame.

South region

Alabama, led by coach Nate Oats in a challenging season, is a No. 1 seed for the first time behind SEC player of the year Brandon Miller, who has armed security on hand after being the subject of threats. The Crimson Tide opened the tourney with an easy win. Potential hurdles could include Baylor or Missouri.

Midwest region

Houston got a top seed and won its opener even though All-American Marcus Sasser is clearly hobbled (strained groin). Potential hurdles could include Penn State, which hammered Texas A&M behind eight 3-pointers and 27 points from Andrew Funk. Former Arizona coach Sean Miller has Xavier in the tourney, too.

West region

Kansas is the top seed in a stacked region and the Jayhawks pulled away from Howard in their opener to advance to a tantalizing second-round matchup against Arkansas. No. 2 seed UCLA looked every bit a title contender in its opener. And you may remember VCU becoming the first NCAA tourney team to forfeit a game because of COVID-19 two years ago; the 12th-seeded Rams are back for a first-round game against Saint Mary's.

Shining moments

Princeton and the Paladins grabbed the spotlight early on opening day and Penn State's Andrew Funk said goodnight with a spectacular shooting display.

The Ivy League's Tigers used a late run to earn their first NCAA Tournament win in 25 years, ousting No. 2 seed Arizona, 59-55. By then, the Paladins were already celebrating Furman's first tourney appearance since 1980 with a win over No. 4 seed Virginia, 68-67, on a deep 3-pointer by JP Pegues with 2.4 seconds left.

Texas A&M had no answer for Penn State's stifling defense and 3-point acumen of Funk, who hit 8 of 10 from deep to help send the Aggies home.

Games to watch

No. 4 Tennessee (24-10) vs. No. 5 Duke (27-8), Saturday, 2:40 p.m. ET, CBS

The Blue Devils have won 10 straight under first-year coach Jon Scheyer with Jeremy Roach matching his career-high with 23 points in each of his last two games. The Volunteers blew an 18-point lead and survived a challenge from Louisiana-Lafayette 58-55 in the opening round.

READ MORE: Alabama basketball freshman star Miller in alleged role for fatal shooting

No. 7 Missouri (25-9) vs. No. 15 Princeton (22-9), Saturday, 6:10 p.m. ET, TNT

Ryan Langborg made Princeton the underdog darlings of this year's tournament. giving the Tigers their first lead with 2:03 to play and the Tigers used a late-game 9-0 run to earn their first NCAA Tournament win in 25 years with an upset of No. 2 seed Arizona. The other Tigers ended a six-game tournament skid with their first win in the Big Dance since beating Clemson in the first round in 2010.

Go deeper

Gun violence has cost lives and disrupted college sports all season, touching some of the top programs in college basketball, including Alabama. Coaches have been thrust into uncertain and unwelcome roles in trying to navigate the topic — as well as the fallout from the Supreme Court decision to overturn Roe vs. Wade.

On a lighter note, if you feel you know March Madness pretty well, try this 25-question trivia quiz put together by AP.

Players to watch

The NCAA Tournament is filled with great players and the AP All-America team is a good place to get familiar with the names. It's also an event where guys you've never heard of — no offense, Drake — can take a star turn. Guard play is always going to be important (see: Baylor, 2021 title winner) and there are some NBA prospects in the mix.

Bet on this, too: Some player — maybe more than one — will have a chance to join the mustachioed Doug Edert (remember Saint Peters' inspiring run last year?) and find a way to cash in on their celebrity.

Betting guide

Who's going to win the national championship? The betting favorites this week to reach the Final Four are Houston, Alabama, Purdue and either Kansas or UCLA, according to FanDuel Sportsbook.

March Madness calendar

Selection Sunday set the bracket matchup s for the First Four and first- and second-round games that stretch from Florida to California. Sweet 16 weekend will see games in New York City (East Region), Las Vegas (West), Kansas City, Missouri (Midwest), and Louisville, Kentucky (South).

Where is the Final Four? In Houston, on April 1, with the championship game on April 3. Basketball aficionados, take note: The women's NCAA Tournament will hold its Final Four in Dallas, a four-hour drive up the road from Houston.

Can't get enough March Madness? Well, there is talk about expanding the tournament despite a host of challenges. Enjoy the 68-team version for now!