This story was originally published by Mother Jones and is reproduced here as part of the Climate Desk collaboration.

Caroline Weinberg, Valorie Aquino, and Jonathan Berman met online after Berman, a post-doc in physiology, created a Facebook group and web page to galvanize some of the protest energy among scientists after Trump’s inauguration. The three, who were in New York, New Mexico, and Texas, thought that scientists should organize a march to “call for science that upholds the common good and for political leaders and policy makers to enact evidence-based policies in the public interest.” Weinberg, a public health writer and researcher, and Aquino, who was finishing her Ph.D. in anthropology, volunteered to coordinate the planning. Almost overnight, the march became a viral social-media campaign.

The culmination of all their work will occur on Saturday, April 22, when the three volunteer cochairs of the March for Science will witness the results of their first experiment in grassroots organizing — with anticipated crowds of hundreds of thousands of people in Washington, D.C., and satellite marches in some 500 cities around the world, including in the Republican strongholds of Wyoming, Idaho, and Oklahoma.