All is not as it appears to be here at Pando, in Utah"s Fishlake National Forest. At first glance, visitors likely see a massive grove of quaking aspen trees, their leaves dancing in the wind. But Pando is not many trees; instead, it"s a single organism. Like many aspen groves, the 40,000 trees in Pando are genetically identical cloned stems that sprouted from the same root system. First discovered in 1968, Pando made waves in the scientific world. It"s become recognized as one of the heaviest known organisms—weighing 6,000 metric tons—and one of the oldest known living organisms. Scientists estimate its root system is upwards of 80,000 years old, having endured the last ice age and countless forest fires. It got to be so old partly because most of the organism is protected underground. So, while an individual stem can die, the organism as a whole survives.