Very few organic materials survive more than a few thousand years at most before decaying away completely. Fortunately for science, however, the original materials of ancient organisms are sometimes replaced by others during fossilization and petrification, as in this example of a piece of petrified tree trunk found in Kwazulu and dating back about 100 million years. Here, the wood of the tree has been replaced by silica, perfectly preserving the original structures present in the tree when it was alive.