Scientists and science advocates are expected to fill the streets of more than 500 cities across the world on Saturday in support of scientific research, which they feel has increasingly come under attack, especially during the Trump administration.

Since its inception in late January, the March for Science has transformed from a grass-roots social media campaign into a bona fide force of scientific advocacy, attracting support from more than 220 official science organizations. But the marchers and the activists who organized them will soon have to address what follows the demonstrations. In addition to channeling the energy they’ve built, they will also need to contend with tensions that have emerged within the scientific community over this political turn.

“We have no intention of letting this stop after April 22,” said Dr. Caroline Weinberg, a public health researcher and co-chairwoman of the march. “I will have considered it pretty much a failure if after April 22 all of this movement and all of this passion dissipates.”

Most eyes will be on Washington, where the main march will occur. But there will also be rallies in medical hubs like Boston, technology centers like San Francisco and even in the heart of oil and gas country, Oklahoma City. The strength of these satellite events could be important indicators of where the activism generated by the march will head in the future.