Remember biology class? Plants, like grass, need light in order to produce chlorophyll, which turns them green. The more light, the greener the grass becomes. The less light, the more yellow the grass becomes. Exploiting this botanical phenomena, British artists Dan Harvey and Heather Ackroyd of Ackroyd & Harvey created these large-scale grass portraits . . . → Read More: Portraits on grass by Ackroyd & Harvey