This book focuses on the symbiotic microbiomes of invertebrates in coral reefs, especially sponges and corals. It provides in-depth and up-to-date reviews on the microbial structure and diversity, metabolism and function, symbiosis and coevolution, environment and adaption, and bioactive potentials. Meanwhile, the future perspectives will be discussed according to the existing problems and the development trend. This book will be of particular interest to the professionals in marine ecology, marine biotechnology, as well as medicinal chemists and molecular biologists.