You’ve heard of disappearing ink, but this pen does the opposite—by creating illustrations with living ink, they only become visible after spending a few days in the sun.

The secret behind this tricky art tool is the special ink made from living algae and cyanobacteria. When artists first put the pen to paper, the living ink isn’t visible to the naked eye. It’s only after prolonged exposure to sunlight that the algae and bacteria start to rapidly multiply to the point where the green chlorophyll becomes abundant enough to see.

The pen also includes regular disappearing ink to help guide artists through their initial sketches. Users can draw with the pink “fast ink” pen in tandem with the blue “slow ink” pen to create different components that reveal themselves at different times. The illustrations grow in a miniature greenhouse, which is actually a glass frame filled with a nutrient-rich material called agar. The fast sketches become visible in one-to-two days, while the slow ink appears after about a week.

Even once the algae and cyanobacteria have died, the stain left by the chlorophyll remains vibrant for years to follow. And while the pens aren’t available for commercial purchase just yet, anyone can pledge to the Kickstarter campaign and reserve a Living Ink set of their own. The pen package is $30, and the special “artist edition" package includes paintable inks and paintbrushes for a pledge of $60 or more. If the campaign reaches their funding goal of $15,000 before January 13, rewards can be expected to ship by June of next year.

[h/t: Gizmodo]