The NCAA Basketball Tournament is the most unpredictable major sporting event.

It involves 68 teams, many of whom didn’t play one another during the regular season, in a single-elimination format.

Unlike in the NBA, where teams prove themselves over the course of a seven-game series, every game in college basketball’s postseason determines which team will go home and which will advance. And unlike in college football, where the nation’s best teams don’t have to take on challengers from lesser conferences, the top college hoops teams must prove that they can outlast the champion of the Sun Belt or the MAC in a one-game, winner-take-all playoff.

Because of the NCAA Tournament’s 68-team, survive-and-advance format, the tourney serves as an incubator for upsets. There are no givens.

The nation’s best team can see its season end at the hands of a 9 seed on the tournament’s first weekend. And an 11 seed whose inclusion in the field baffles analysts can advance to the Final Four.

Anyone can beat anyone. And the unlikely wins are what makes March so mad.

So, to get you ready for this year’s tourney, which begins tonight in Dayton, here are 16 of the greatest upsets from the modern era of the NCAA Tournament:

16. (13) Valparaiso 70, (4) Mississippi 69; 1998 First Round

In terms of seeding and talent differential, this upset isn’t on the same level as some of the others on this list. But few upsets have ended in such a memorable fashion.

Valparaiso, the 21-9 champions of the Mid-Continent Conference, kept the game close for 40 minutes. With ten seconds remaining, the Crusaders had the ball, trailing by two. Star guard Bryce Drew, son of coach Homer Drew, missed a three-pointer that would have given Valpo the lead.

Related: See where this moment falls on our list of the 10 Most Memorable March Madness Moments Ever.

Instead, Mississippi came away with the rebound, and Valpo fouled Ole Miss forward Ansu Sesay. Sesay, normally a very good free-throw shooter, missed both shots. In a scramble for the ball following the second miss, Mississippi’s Keith Carter knocked the ball out of bounds, giving Valparaiso possession with 2.5 seconds on the clock.

The Crusaders threw a cross-court pass to Bill Jenkins, who tipped the ball to Drew, who nailed a three-pointer as time expired to give Valpo a 70-69 win.

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The Crusaders beat Florida State in the second round then lost to Rhode Island in the Sweet Sixteen.

15. (14) Chattanooga 73, (3) Georgia 70; 1997 First Round

The University of Tennessee at Chattanooga is best known as the alma mater of Terrell Owens and Dennis Haskins, the actor who played Mr. Belding on Saved by the Bell. But in 1997, the Chattanooga Mocs were known for basketball. (Haskins actually played basketball for the Mocs in the late 1960s and early 1970s.)

Chattanooga, who won the Southern Conference championship with an overall record of 22-10, opened against a Georgia team that went 24-9 in a stacked SEC East. Mr. Belding’s Mocs prevailed, beating Tubby Smith’s Bulldogs 73-70.

Chattanooga would upset sixth-seeded Illinois in the second round before losing to Providence in the Sweet Sixteen.

14. (14) Austin Peay 68, (3) Illinois 67; 1987 First Round

Prior to the 1987 tournament, ESPN’s Dick Vitale had declared Illinois his sleeper pick. The third-seeded Illini’s roster included future first-round NBA draft picks Ken Norman and Kendall Gill along with talented seniors Doug Altenberger and Tony Wysinger. Austin Peay, on the other hand, had started the season 10-10 and managed only an 8-6 record in the Ohio Valley Conference.

The 14th-seeded Governors trailed for much of the first half but managed to tie the game at 32 going into the intermission. When Austin Peay took a second-half lead, Vitale—from the ESPN studio in Connecticut—remarked that he would stand on his head if the Governors ended up winning the game. The Illini nearly spared Vitale the indignity of doing a head-stand when Wysinger hit a jumper with 13 seconds remaining to give Illinois a one-point lead.

The Governors opted not to call time out and managed to get the ball to Tony Raye under the basket with two seconds to go. Norman had no choice but to foul. Raye sank both free throws to give Austin Peay the win.

Vitale made good on his promise and did the head stand, with some assistance.

Continue reading to relive a moment Indiana fans would just as soon forget, a “miracle” that Kansas fans would love to relive, and to see a classic picture of Dale Brown “cutting” down the nets…with no scissors necessary.