Abstract
We are all familiar with the animals and plants on land, as well as plankton, fishes and whales of the world oceans; however, a new biological realm is coming into focus: that of life in the rocks. The rocks of the crust of the earth, especially the deeper ones, are relatively inaccessible. "Out of sight - out of mind" certainly applies here; and it is not surprising that although we have known of some life in deep rocks for decades, only recently have scientists given serious attention to this hidden biological realm.