Grass photographs.

Heather Ackroyd and Dan Harvey [...] have perfected their talent for manipulating the light sensitivity of ordinary grass. Black and white negatives are projected onto the grass, 12 hours per day, for over a week as the grass grows in a dark room. Different blades get different exposure and the results are photographs, like the recent Wimbledon portraits shown above.

Veer: Ideas: Wimbledon grass photographs by Anders J. Svensson