A blister is a bubble of fluid under the skin. The clear, watery liquid inside a blister is called serum. It leaks in from neighboring tissues as a reaction to injured skin. If the blister remains unopened, serum can provide natural protection for the skin beneath it. Small blisters are called vesicles. Those larger than half an inch are called bullae. A blood blister is filled with blood, rather than serum.
With 15,145 people, Cullman is the 41st most populated city in the state of Alabama out of 578 cities. But watch out, Cullman, because Alexander City with 14,849 people and Scottsboro with 14,748 people are right behind you.
It is the principal city of the Tuscaloosa Metropolitan Statistical Area, which includes Tuscaloosa, Hale and Pickens counties and has an estimated metro population in 2013 of 235,628. Tuscaloosa is also the home of The University of Alabama, Stillman College and Shelton State Community College.