It is an extraordinary experience to observe the different mechanisms and structures of all living things that we constantly interact with. While examining this book, which deals with different structures in many different living groups, I am sure that you will gain different perspectives on your current knowledge. This book, which consists of 5 chapters prepared by different researchers who are experts in their field, contains very important information on various subjects from humans to plants and insects. In science where multidisciplinary work always leads to more productive results, I hope that there will be many scientists and young people interested in science who will benefit from this book. I would like to thank the staff of ISPEC publishing house for their devoted work, who brought together valuable scientists and scientists for the creation of this book.