The battery, the first major portable energy packet in the last few billion years. When simple prokaryotes acquired mitochondria several billion years ago, these amazingly efficient portable energy devices opened up Design Space to multicellular life of dazzling variety. Many metazoa developed complex nervous systems, which gave the planet eyes and ears for the first time, expanding the epistemic horizons of life by many orders of magnitude. The modest battery (and its sophisticated fuel cell descendants), by providing energy for autonomous, free-ranging, unplugged artifacts of dazzling variety, is already beginning to provide a similarly revolutionary cascade of developments. Politically, the transistor radio and cell phone are proving to be the most potent weapons against totalitarianism ever invented, since they destroy all hope of centralized control of information. By giving every individual autonomous prosthetic extensions of their senses (think of how camcorders are revolutionizing scientific data-gathering possibilities, for instance), batteries enable fundamental improvements in the epistemological architecture of our species. The explosion of science and technology that may eventually permit us to colonize space (or save our planet from a fatal collision) depends on our ability to store and extract electrical power ubiquitously. Our batteries are still no match for the mitochondrial ATP system — a healthy person with a backpack can climb over mountains for a week without refueling, something no robot could come close to doing — but they open up a new and different cornucopia of competences.