This is a piece of one of the largest and longest-lived life forms on Earth. The giant sequoia tree from which this slice comes survived for over 1,300 years in what is now called the Sierra Nevada range of California. The full height of the tree, which was felled by lumberjacks in 1891, exceeded 300 feet. There are even bigger giant sequoias.

Forests of many kinds of sequoias were widespread in the age of dinosaurs and continued to flourish for tens of millions of years thereafter. Then mountains like the Sierra Nevada rose, and the climate in most regions beyond became too cold for sequoias. By the onset of the Ice Ages, approximately one million years ago, they had vanished from most of the Northern Hemisphere. Today the only sequoia species left are the giant sequoia, of the Sierra Nevada in central California, and the very different coast redwood, along the coast of northern California and southern Oregon. Together with a few Asian relatives and the bald cypresses of North America, they are all that remain of the once much larger and more widespread redwood family.

Several factors contribute to the long life of the giant sequoia. Its unusually thick bark is fire-resistant; the trees actually depend on fires to thin out the firs and pines that would otherwise eventually take over. Giant sequoia seeds do well in a fire-mineralized soil and are shed in greatest numbers after a fire. The tree also contains a natural wood preservative, and is very resistant to disease. No one knows how long a sequoia can live. Many trees in Sequoia National Park, in California, are more than 3 ,000 years old, still growing vigorously and producing abundant seeds every year.

This sequoia slice offers a lesson in how to discover the age of a tree. Around the central point of the slice are concentric rings, some of which are invisible to the naked eye. Each of these represents one year's growth. To make the immense age of the tree more vivid, we have placed marks on some of the growth rings, each corresponding to a significant historical event. Even 1,000 years ago, represented by the fourth mark from the center, this was a very big tree.

These rare and remarkable trees are a natural treasure. Most of them are in Sequoia and Kings Canyon National Parks or under other government protection. Today, it is illegal to cut them down.