You may be familiar with the red furry balls that you get on wild roses but did you know that they are formed by the plant in reaction to a tiny parasitic Bedegaur gall wasp setting up home? Inside the 'cushion' there will be many tiny chambers and within each one an egg is laid.
Amazingly (and a first for me) I managed to find one with a eenie-weenie wasp just emerging! my thumbnail should give you some idea of the scale!