Michelle Obama recently shared a valuable advice to millennials that use social media to get their messages across.

While at the inaugural youth leadership summit, the former first lady stressed the fact that “words matter.” However, Obama clarified that this doesn’t mean anyone can just post all their thoughts on social media, most especially Twitter.

“When you have a voice, you can’t just use it any kind of way, you know? You don’t just say what’s on your mind. You don’t tweet every thought. Most of your first initial thoughts are not worthy of the light of day,” she said.

The wife of former President Barack Obama also said that social media, like Twitter, has been handed over the kids who may not be responsible enough to realize the power of their words. “You need to think and spell check it right and have good grammar,” she advised.

Obama also used herself as an example of someone who has the power to inspire or offend others on social media. After all, the platform is dubbed as a “powerful weapon.” “When you’re the first lady or the president, or the commander in chief, and you have that voice and that power and that platform, what comes with that responsibility to know that every word you utter has consequences,” she said.

Meanwhile, Obama also used the opportunity to weigh in on the recent sexual harassment cases that have come to light in the country. “When we think about women in particular we ask them to speak up. We ask them to speak their mind. We ask them to just say no, to speak out against sexual harassment. But if we don’t teach our young girls to speak at an early age, that doesn’t just happen. It takes practice to have a voice. You have to use it again and again before you can say ‘no’ or ‘stop,’ ‘don’t touch me,’” she said.

According to People, the event organized by the Obama Foundation was attended by 500 youth participants and 60 countries. Other speakers at the inauguration in Chicago included Prince Harry and Lin-Manuel Miranda.