Oak Galls

Struggled for a blip today, saw these on an oak tree.
Googled info.
Galls are abnormal growths or swellings of plant tissue often caused by the attack of an insect. Galls on oaks are most often caused by small wasps or midges. Insects that cause galls to form are known as gallmakers. Galls grow to surround the tiny insects that form them and provide them with protection from weather, predators and parasites. The gall also provides a source of food for the insect. The insect develops and grows inside the gall during the summer and emerges as an adult either in the summer or the following spring.