What to know now:

1. Brussels attacks:  A day after 31 people were killed and more than 200 wounded in explosions in Brussels, Belgian officials say two brothers, Khalid and Brahim El Bakraoui, were responsible for the attacks. The  two  were seen on video pushing a cart in the Brussels airport. They were killed in the explosions. Belgian media is reporting that a third person involved in the bombings has been arrested.

2. Tuesday's primaries: Hillary Clinton and Donald Trump won the ArizonaDemocratic and Republican primaries Tuesday, while their  opponents, Sen. Bernie Sanders and  Sen. Ted Cruz, won delegates in Utah.  In Idaho, where a record was set for the single largest U.S. caucus ever held, Sanders took home the prize.

>> Read more trending stories  

3. Trump vs. Cuz, round 2: Donald Trump  and Ted Cruz exchanged words via Twitter over their wives Tuesday night. Trump tweeted that Cruz used a nude photo of Trump's wife, a former model, in an ad against him. "Lyin' Ted Cruz just used a picture of Melania from a G.Q. shoot in his ad. Be careful, Lyin' Ted, or I will spill the beans on your wife!". Cruz responded, saying the ad was not from him. "Pic of your wife not from us. Donald, if you try to attack Heidi, you're more of a coward than I thought. #classless."

4.  Jeb endorses: Former Florida Gov. Jeb Bush has announced he will endorse Sen. Ted Cruz for president. Bush, who dropped out of the race in February, had a contentious relationship with Donald Trump who often called him "weak." Though out of the race, Bush  has picked up some delegates in early primaries and early voting.

5. Bachelor contestant killed:  A contestant from "The Bachelor" was killed in  a plane crash in California Monday. Erin Storm, 41, who took part in the ABC dating show during Season 12, was the pilot of a small plane that crashed after takeoff from Hawthorn Municipal Airport in California. Storm was flying an Airborne XT-912 ultralight plane.

In case you missed it

Former Alaska Gov. Sarah Palin is making a pilot for a new show featuring her as a judge in a courtroom setting. According to the production company working  on the project, Palin hopes to get a sponsor for the show to sell in syndication. Palin has no legal training.

Ever wanted to be a millennial? Here's  a guide.