Book excerpt: The Mediterranean Sea is considered the most threatened sea on Earth. This book presents a scientific look at the past, present and future changes occurring in the Mediterranean Sea. In addition, this book also gives a background description of the geology, physical oceanography, marine chemistry and marine biology of the Mediterranean Sea. It provides an up-to-date summary of the human (anthropogenic) factors affecting the Mediterranean marine environment, as well as an estimate of the future of the Mediterranean Sea as related to local and global changes, with an emphasis on climate change.