Almost half of your body is muscle. There are more than 650 muscles, and they make up about 50 percent of total body weight.

The biggest muscle in the body is the gluteus maximus - the butt. Each of these two muscles tips the scales at about two pounds (not including the overlying fat layer). The tiniest muscle, the stapedius of the middle ear, is just one-fifth of an inch long.

Most cells in the body are microscopic in size, but muscle cells, also called muscle fibers, can be up to 1 foot long and visible to the naked eye.