The Best Things Come in Small Packages
Pluck a hair from your head. (Really.) Now look at it. It isn't very thick, is it? Well, to a microprocessor manufacturer, that hair looks like a telephone pole. That's because a hair is more than 2000 times wider than a transistor on a microprocessor. Wires between transistors are even thinner. They're more than 4000 times thinner than a hair.
How big is a human hair? About 100 microns in diameter. That means a transistor is just 0.045 microns wide.
What's a micron? It's a very small metric measurement. You're probably familiar with centimeter marks on a ruler. (If not, go look at one.) A micron is .0001 of a centimeter.
A microprocessor transistor then is 0.0000045 centimeters wide. (Want that in inches? It's 0.00000177 of an inch.)