Bioengineers Kikolai Braun and Kiera Havens have taken hacking to a new level through the creation of a new breed of petunia that can change from white to red, and back again, on cue. Watering the miracle flower with diluted ethanol solution, such as old beer, the flower will change colour from white to red over 24 hours but when watered with regular water the plant will reverse it pigment change and return to white.

See it here.