Thousands took to the streets Saturday to support science. They brought some very good signs.

Thousands of people took to the streets in over 600 cities Saturday as part of the March for Science, organized to celebrate science’s contributions to the public good. (Scroll down for some of the best signs from the march.)

In Chicago, authorities estimated that over 40,000 people joined the march — it was so big that at noon, police advised protesters not yet at the march to stay home. In New York, there were likely more than 20,000 people in attendance. In Los Angeles, authorities estimate that 10,000 people showed up.

While officially nonpartisan, the motivations behind the march were undoubtedly political, a response to the Trump administration’s anti-science rhetoric and policy moves. President Trump’s positions on climate change, the cuts to scientific agencies in his budget proposal, and his insistence, despite all evidence to the contrary, that vaccinations are linked to autism, have caused deep concern in the scientific community and among the public.

In Washington, D.C., thousands gathered on the misty grounds of the Washington Monument to hear speakers at a four-hour rally, chanting “Hey, Trump, have you heard? You can’t silence every nerd” and “Build labs, not walls,” according to the Washington Post.

Referring to Trump as “that guy over there,” Questlove subtly raised his middle finger in the direction of the White House, adding, “It’s been frustrating to watch as certain forces in our society try to squelch science,” CNN reports.

“Science must shape policy. Science is universal. Science brings out the best in us,” science educator Bill Nye said in his speech as the rain cam down. “With an informed, optimistic view of the future, we can — dare I say it — save the world!” The crowd erupted in cheers.

Rallies took place on six continents Sunday, and a team of researchers on Antarctica expressed their solidarity on social media. Here are a few of the best signs from the marches: