Bald faced hornet nest (Dolichovespula maculata). Virginia.   

I noticed a small hornet nest under an overhang on my house last spring — I think it was about the size of a child’s fist. 
Photo of wasp nest split in two showing interior cells
Bald-faced hornet nest.  The entrance is at the bottom left and bottom
right (it is cut in half.)
One day I trotted across my deck and apparently made too much noise because a couple of wasps came flying out and bumped my head.  They didn’t sting me but made it very clear that I needed to pay attention in the future. 
I walked more quietly after that and warned visitors to be careful. The nest grew to be almost exactly 10” long. (25.4cm) over the summer. 
I removed it in January once the hornets had all died (except, possibly, for a queen carrying fertile eggs who would have left the nest and found a tree hollow or similar place to overwinter.)  When I got stuck inside during a snowstorm and was desperate for something to photograph, I sliced the nest in two, and that's what you see.
These wasps are omnivores — adults may prey on other insects, scavenge dead creatures, carry away food discarded by humans, and so on. They also act as pollinators when they feed on plant nectar. The wasp’s reproductive cycle is somewhat similar to that of other social wasps and bees -- quite complicated.  Google it for a good read.
I thought the inside of the nest was interesting.  You can see the cell structure quite clearly, and it is an engineering marvel!

Shot with Olympus OM-D E-M1ii and Olympus 12-40mm. TT350 Godox flash with DIY diffuser