The physical part of a chip that contains the transistors, resistors and capacitors, which perform computing and storage operations; the "action area." Only a few micrometers thick, the active area lies within the border of pads to which are bonded the wires that connect the chip to the chip package and then the circuit board.

The Incredible Chip
No man-made object is perhaps more incredible than the chip, the largest of which has an active area the size of a postage stamp, except that the stamp is many times thicker. In one of today's high-speed CPUs, millions of transistors open and close collectively more than 40 quadrillion times per second. Think about it! Forty quadrillion openings and closings per second, second after second, minute after minute, hour after hour, in perfect digital precision and synchronization. One quadrillion is 10 million times a million.