"It's what grows in the ponds, the lakes, the oceans," said Living Ink Technologies co-founder and Colorado State University PhD candidate, Scott Fulbright.
He says the green stuff could change the way we think about ink.
"Nature provides a lot of bio-diversity for us to work with," he said. "I can send you a greeting card where some of the letters pop-up and then the next day some more letters pop-up. You have to guess what it says by the end of the week after the whole message grows."
It's a message that only appears when the recipient hangs the card in the sunlight.
Fulbright and his business partner, Steve Albers, won first prize at the University of Colorado Denver's Entrepreneurship Business Plan Competition. They hope to cash-in on the $8 billion greeting card industry and one day take on commercial printers with safe, renewable algae-derived ink.
"It saves the consumer potentially a lot of money, and if it takes off it has the potential to revolutionize the ink industry," said Madhavan Parthasarathy, Associate Professor at the CU Denver Business School
Living Ink will be launching a Kickstarter campaign mid-August for their stem algae coloring books.