Bacteria are extremely small living things. While we measure our own sizes in inches or centimeters bacterial size is measured in micorons. One micron is a thousandth of a millimeter a pinhead is about a meter across. Rod shaped bacteria are usually from two to tour microns long, while rounded ones are generally one micron in diameter Thus if you enlarged a founded bacterium a thousand times, it would be just about the size of a pinhead. An adult human magoified by the same amount would be over a mile (1.6 kilometers) tall