Well to start - 12 states and one U.S. Territory will be deciding who they want to run for president.
And more delegates are at stake on March 1st than any other day of the primary election season.
You may have heard people call Super Tuesday the "SEC primary", and here's why:
Alabama, Arkansas, and Texas joined Super Tuesday this year, which already included Georgia and Tennessee. Fans of college sports will no doubt see the pattern.
In these southern states, both Democrats and Republicans will vote.
Also holding primaries for both parties - Massachusetts, Minnesota, Oklahoma, Vermont and Virginia.
Alaska will hold its Republican caucus while Democrats caucus in American Samoa.
Colorado is unique - caucusing for both parties, but its Republican delegates won't decide until the national convention.
Now - about those delegates… On Super Tuesday, 595 Republican delegates are at stake - almost half of what the winner needs to clinch the nomination.
Democrats will split 1,004 delegates, again about half of what's needed to secure the nomination.
So here's what to look for:
As the Democratic contest heads South, Hillary Clinton's advantage among African-American voters could make the difference and give her a lead Bernie Sanders can't close.
If Clinton doesn't sweep the South, it will be a major upset.
Sanders expects to do well in Vermont, which he has represented in Washington for 25 years.
On the Republican side, pressure is on Ted Cruz to win his home state, Texas, where he's a freshman US Senator.
If front-runner Donald Trump does as well on Super Tuesday as he did in South Carolina and Nevada, his lead will grow quickly.
What makes #SuperTuesday so super? Well to start, 12 states and one U.S. territory will be deciding who they want to run for president. And more delegates are at stake on March 1 than any other day of the primary election season. Read more: http://bit.ly/1LQG5cH