This book aims to contribute toward a proposal to set up a very low frequency (VLF: 30 MHz) radio observatory on the lunar surface. The primary motivation for this proposal is to learn about our universe through a completely new spectral window in astronomy by taking advantage of the unique lunar environment. The secondary motivation is to take on a challenge of building and operating a facility on the Moon, especially through international cooperation, and to inspire people when they look at the Moon. After explaining these motivations and reviewing previous efforts toward this cause, this book examines unsolved questions about the advantages of the lunar environment, proposes a preliminary observatory to be set up at the lunar south pole, and identifies desirable measurements to be made at the earliest opportunities.