Here's how it works: Go to #GlobalSelfie Signs for Download (.PDF) to download a printable NASA sign, snap a photo of yourself holding it wherever you are, then post it on one of five social media websites, including Twitter, Instagram, Facebook, Google-Plus and Flickr, and use the hashtag #GlobalSelfie.
NASA will then use those photos to create a mosaic image of Earth as part of its "Earth Right Now" campaign.
Earth Day was instituted in the United States in 1970 in an effort to raise environmental awareness in the country.
