As semiconductor manufacturers build ever smaller components, circuits and chips at the nano scale become less reliable and more expensive to produce – no longer behaving like precisely chiseled machines with tight tolerances. Modern computing tends to ignore the variability in behavior of underlying system components from device to device, their wear-out over time, or the environment in which the computing system is placed. This makes them expensive, fragile and vulnerable to even the smallest changes in the environment or component failures. The Variability Expedition envisions a computing world where system components -- led by proactive software -- routinely monitor, predict and adapt to the variability of manufactured systems. The Variability Expedition proposes a new class of computing machines that are adaptive but highly energy efficient. They will continue working while using components that vary in performance or grow less reliable over time and across technology generations. A fluid software-hardware interface will mitigate the variability of manufactured systems and make machines robust, reliable and responsive to changing operating conditions -- offering the best hope for perpetuating the fundamental gains in computing performance at lower cost of the past 40 years.