This article and images are making the rounds on the interwebs, but I could not help but share how absolutely amazing they are.  If you haven't read the story (link below) or seen the images, there are some anonymous artists (Dangerdust) who sneak into classrooms and create these pieces of art.  They are truly astounding, beautiful, and absolutely insane that people have created these with just a chalkboard and chalk.  I encourage you to take a look and follow them on instagram.