UK artists Heather Ackroyd and Dan Harvey took advantage of the natural photosensitive nature of grass to use them as pixels in what we can only call a "photograss."
CR Blog has more on this particular set of photos, commissioned by HSBC in partnership with the 2008 Wimbledon Tennis Championships:
“When grass gets plenty of sunlight, it produces chlorophyll and therefore turns green – but the less light it receives, the more yellow the colour is,” explains JWT art director Mark Norcutt of the process used to make the work. “Heather Ackroyd and Dan Harvey discovered that by projecting a bright black-and-white negative image onto a patch of grass as it grows (in an otherwise dark room), they can use the natural photosensitive properties of the grass to reproduce photographs. From a distance it looks like any other monochrome photograph (albeit with a slightly unusual tint); up close, it looks like perfectly ordinary grass. But even individual blades sometimes have a range of hues, as any given cell can respond to the amount of light it receives.”
Link - Thanks sadtomato!
Previously on Neatorama: Photosynthetic Photography: Pixels are Blades of Grass, also by the two artists.