I found this growing on a neighborhood tree & brought it home to photograph. As a kid growing up in NYC, we used to call these "itchy balls", because we would grind them up into what we called "itchy powder" & (as pranks) put them down each other's shirts, which would cause our backs to itch like crazy. Kids sometimes do really stupid things, don't they? I never learned what they really were until just now, when I did a google image search & found out that they are the fruit of the sweet gum tree: "Liquidambar styraciflua, commonly called American sweetgum, sweetgum, sweet gum, sweet-gum (sweet gum in the UK), hazel pine, American-storax, bilsted, red-gum, satin-walnut, star-leaved gum, or alligator-wood is a deciduous tree in the genus Liquidambar native to warm temperate areas of eastern North America and tropical montane regions of Mexico and Central America. Sweet gum is one of the main valuable forest trees in the southeastern United States, and is a popular ornamental tree in temperate climates. It is recognizable by the combination of its five-pointed star-shaped leaves and its hard, spiked fruits. The distinctive compound fruit is hard, dry, and globose,1–1.5 inches (25–38 mm) in diameter, composed of numerous (40-60) capsules. Each capsule, containing one to two small seeds, has a pair of terminal spikes (for a total of 80-120 spikes). When the fruit opens and the seeds are released, each capsule is associated with a small hole (40-60 of these) in the compound fruit. Fallen, opened fruits are often abundant beneath the trees; these have been popularly nicknamed "burr (or bir) balls", "gum balls", "space bugs", "monkey balls", "bommyknockers", "sticker balls", or "goblin bombs". The fruit is a multicapsular spherical head and hangs on the branches during the winter. The woody capsules are mostly filled with abortive seeds resembling sawdust. The seeds are about one-quarter of an inch thick, winged, and wind-dispersed. Goldfinches, purple finches, squirrels, and chipmunks eat the seeds of the tree. The seeds stratify within 30–90 days at 33°–41 °F or soaked in water for 15–20 days. The long-stemmed fruit balls of Liquidambar resemble those of the American sycamore or buttonwood (Platanus occidentalis), but are spiny and remain intact after their seeds are dispersed; the softer fruits of Platanus disintegrate upon seed dispersal. The long-persisting fallen spiked fruits can be unpleasant to walk on; sweet gum is banned in some places for this reason. In abundance, they can leave a lawn lumpy."