Former first lady Michelle ObamaMichelle LeVaughn Robinson ObamaObamas are 'most admired' man and woman in world: poll John Legend: Americans may have to think about leaving country if Trump reelected Black stars reimagine 'Friends' to get out the vote MORE sent a message of encouragement to 16-year-old Swedish climate activist Greta Thunberg early Friday morning after she faced ridicule from President TrumpDonald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE, telling the teenager to “ignore the doubters.”

@GretaThunberg, don’t let anyone dim your light,” Obama tweeted.  “Like the girls I’ve met in Vietnam and all over the world, you have so much to offer us all. Ignore the doubters and know that millions of people are cheering you on.”

Obama recently traveled to Vietnam with actress Julia Roberts as part of the Obama Foundation’s Girls Opportunity Alliance program, which seeks to empower adolescent girls around the world through education. 

Trump tweeted Thursday that it was “ridiculous” that Time magazine chose Thunberg as its 2019 “Person of the Year,” an honor he was shortlisted for. Trump wrote that the teenager needed to “work on her Anger Management problem.” 

“Chill Greta, Chill!" Trump added.

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The president’s eldest son, Donald Trump Jr., also criticized the outlet for selecting the activist he said has been used “as a marketing gimmick” instead of pro-democracy activists in Hong Kong. 

Thunberg did not directly address the president’s comments but changed her bio on Twitter to describe herself as a "teenager working on her anger management problem."

Trump's attack sparked backlash from Democratic lawmakers and presidential candidates, including former Vice President Joe BidenJoe BidenFormer Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick Bloomberg rolls out M ad buy to boost Biden in Florida MORE.

“What kind of president bullies a teenager?” the front-runner in the Democratic primary wrote.

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The #BeBest hashtag from f irst lady Melania TrumpMelania TrumpWatchdog confirms State Dept. canceled award for journalist who criticized Trump Ginsburg becomes the first woman to lie in state in the Capitol Rabbi memorializes Ginsburg: Her dissents were 'blueprints for the future' MORE’s anti-cyberbullying campaign began trending on social media in the United States as thousands of social media users called on Trump to respond to her husband’s remarks.

The Be Best campaign encourages children to be kind on social media and speak “with respect and compassion.”

Time announced on Wednesday that it was naming Thunberg its Person of the Year for drawing attention to the threat of climate change. She is the youngest person to ever to receive the honor.