There are architectures you see and architectures you don't. ARM is the most extreme case of the second category: it runs in the phone in our pocket, in the home router, in the eighty-euro board that serves as a home server for millions of tinkerers, in the datacentres of Amazon and Google. It is everywhere, and almost nobody knows what it is. It took me years too to bring it into focus, and the occasion was a Raspberry Pi 3 that I had decided to turn into a Nextcloud – the first brick of what would become, in the years to come, my small homelab – many years ago. It was a line in /boot/config that made me notice the thing: the Pi's processor, a Broadcom BCM2837, used the same architecture as the Android phones I had hacked for years. ARM. Same instruction set, same underlying logic, same family.