In a Twitter post the former first lady told Greta to never "let anyone dim [her] light".

Michelle Obama's tweet comes after the incumbent U.S. president, Donald Trump, mocked Greta a day earlier on the social media platform. He insinuated that the activist has mental health problems and said she needs to "chill".

The mocking was spurred on by Greta's recent naming by TIME Magazine as 2019 Person of the Year.

This is not the first time the president of the U.S. has made fun of the 16-year-old activist. In September he sarcastically called her a "happy young girl" after she delivered an emotional speech in front of the United Nations general assembly.

In both instances Greta Thunberg has responded to Donald Trump's comments by mockingly making them her Twitter bio.

Compiled by Phelokazi Mbude

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