In popular cultures, "Extraterrestrials" are life forms — especially intelligent life forms— that are of extraterrestrial origin (often also called "aliens").
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“Who shall describe the inexpressable tenderness and immortal life of the grim forest, where Nature, though it be midwinter, is ever in her spring, where the moss-grown and decaying trees are not old, but seem to enjoy a perpetual youth.”
—Henry David Thoreau (1817–1862)