An acorn is the nut of an oak tree, belonging to the family Fagaceae. It typically has a hard outer shell and contains a single seed. Acorns are an important food source for various wildlife, including squirrels, deer, and birds. They usually fall from the tree in the autumn and can be found on the ground beneath oak trees. Acorns vary in size and shape depending on the species of oak tree. They are often oval or round and can range in color from green to brown. Acorns play a crucial role in the ecosystem, as they can grow into new oak trees when planted in suitable soil.