Centered around the theme of “Lab on/in Fiber,” this book invites several representative research groups in this research field from across China to collaboratively write 12 chapters on their main achievements and important research progress over the years. The book focuses on the technical foundation of building various types of labs on/in fibers and provides practical examples of constructing various micro-labs on/in fibers to illustrate the purpose, methods, and technological approaches of establishing labs on/in fibers.