This book explores the diversity of insects as the biggest and most important animal group on earth. The author estimates there could be around 10 million living insect species today. The book describes the history and evolution of insects, with the oldest insect fossil (the mandible (or jawbone) found in Scotland), estimated to be around 408 to 438 million years old. This shows that insects were one of the earliest animals to conquer the earth. This book explains that insects are indispensable to every ecosystem. They pollinate crops, decompose plants and animals, and are themselves nourishment for some communities. The book identifies various insect habitats, both marine and terrestrial, including how to protect them.