In the 1950s I spent a significant chunk of my pocket money buying a transistor. It was a small metal cylinder (about 5mm in diameter and 7mm deep) with three wires protruding from its base. I needed it for a little radio I was building, and buying it was a big deal for a lad living in rural Ireland. My baffled parents couldn't understand why this gizmo their son was holding between finger and thumb could be interesting; and, to be honest, you couldn't blame them. The A13 processor that powers the iPhone that I used to find a photograph of that first transistor has 8.5 billion of them etched on to a sliver of silicon no bigger than a fingernail – a "chip".