Part 4/10:

At this scale, many of the laws governing larger objects, such as inertia and drag, behave quite differently. For instance, smaller flyers have a much higher surface area relative to their volume, which leads to increased drag and less ability to stay airborne without a higher wing flapping frequency. This means that, unlike birds, these micro-robots utilize rapid wing flapping—hundreds of times per second—to generate the lift they need to carry out their functions.