Willy Wonka gumball? World’s smallest dinosaur egg?
Previously: Fifty Common Plant Galls of the Chicago Area
ETA: Thanks to the lovely website iNaturalist.org, I’ve been informed that the gall may belong to the species Atrusca quercuscentricola, a gall wasp that forms galls on the leaves of post oaks, one of the most common trees in our forest inventory areas.