Trees have three principle features that distinguish them from all other plants. First, they have a woody stem, roots and branches which do not die back in winter, but continue to grow year after year. From the moment of its germination, a tree remains visible; from the tallest Sequoia to the smallest garden fruit tree, this principle of growth remains constant. Second, trees live longer than any other organism on earth. Trees commonly live more than 1,000 years, and many grow considerably older. A bristlecone pine, Pinus longaeva, at Schulman Grove in California has been documented both by core drilling (a pencil-thin core is taken from the tree's trunk, and the rings are counted) and by carbon-dating as being 4,700 years old. Trees have been living on Earth for more than 370 million years, and today can be found almost everywhere from the Arctic Circle to the Sahara Desert.