The flight of insects is a high potential topic for bio-inspired micro flows because of their optimized energy consumption and the economical and innovative construction of the flight apparatus.This book will focus on two closely related aspects of flight in flapping insect wings: Unsteady aerodynamics and energetics. The most recent discoveries on unsteady aerodynamic mechanisms for lift enhancement (vortex theory, rotational flows, energy recycling, and wake-wing interactions) are covered as well as the significance of those mechanisms for flight power requirements and efficiency. Comparisons will be made between experimental data coming from physical robotic wings and numerical models (computational fluid dynamics). The energetics section will dissect the power requirements for flight and show how flight force production is constrained by the maximum mechanical power output of the flight musculature.The over-arching systems-level perspectives and focus on major principles in this book, will be a welcome change from the extensive mathematical descriptions that are typical of other texts and monographs on aerodynamics. The book will thus appeal to both biologists and engineers alike.