While electronics are becoming increasingly power efficient, new opportunities arises in how we deal with power management. Energy harvesting is progessively discovering new possibilities in how we handle power sources. This book handles the growing potentials about using ambient energy sources such as e.g. kinetic movements, solar power and ambient radiation. Whilst these sources are easy to be found in our surroundings, they also mainly only exist in low concentrations of energy for extraction. Combining these easily found energy sources together with a new perspective of energy harvesting introduces a new way to feed power into our circuits.