The internet has been taken over by the color orange on June 1! #WearOrange was a top trend on Friday, with dozens of celebrities rocking the bright color. But what does the popular hashtag mean?

The #WearOrange movement was started by Everytown, an organization that "researches a range of vital issues surrounding gun violence, develops data-driven solutions, and works with lawmakers and people like you to pass common-sense laws and policies that save lives." Since June 1 is National Gun Violence Awareness Day, they figured it would be the perfect day to kick off Wear Orange Weekend, during which events are held around the country to educate people and demand change.

So why do they use the color orange? "Orange is the color that Hadiya Pendleton’s friends wore in her honor when she was shot and killed in Chicago at the age of 15 — just one week after performing at President Obama’s 2nd inaugural parade in 2013," explained the website. "After her death, they asked us to stand up, speak out, and Wear Orange to raise awareness about gun violence."

To show their support, dozens of celebrities including Julia Louis-Dreyfus, Julianne Moore, Nate Berkus, Halsey, and so many more have posted selfies wearing orange shirts, scarves, blazers… anything they could find, really. Scroll through the gallery below to see all the stars that participated in #WearOrange.