The second annual March for Science rallies are a call to action. And a showcase for great signs.

In America and other parts of the world, the scientific community has been under attack — and last year, organizers put together the first-ever March for Science.

Like so many of the rallies that sprang up in the wake of President Trump's election, the first March for Science helped inspire some hilarious and insightful signage that captured a moment in time:

And this year may be even better. On April 14, the second annual series of marches took place and instantly went viral, rising to the top of Twitter and Instagram as people shared stories and pictures of signs from rallies across the globe.

Once again, fans of science got incredibly crafty.

Others made it clear that nerds have excellent senses of humor.

And so do dogs, apparently.

Some made serious points about the importance of science.

While a few let themselves get a little angry.

Some signs were purely inspirational about the power and potential of science.

The main rally was held in Washington, D.C., and quickly spread to more than 600 cities around the world.

Photo by Rajesh Jantilal/Getty Images.

It's a shame that science is under attack. But it's inspiring to see how many people are marching to support those whose work is changing the world for the better.

There's nothing wrong with debate. Challenging assumptions, eliminating false evidence is literally at the heart of the scientific method. Unfortunately, the argument has shifted toward one about the nature of science itself. That's a shame.

Science and technology are arguably the greatest force for good in our world today, affecting virtually every aspect of our lives. Still, the March for Science rallies show that those who support scientific progress aren't about to be pushed out of the conversation.

If you couldn't make it to one of the rallies but still want your voice heard, the scientists have got a solution for you: