This lecture covers the development and applications of fiber Fabry-Perot (FFP) microcavities, focusing on their features and various uses in research and technology. The instructor, Prof. Jakob Reichel, discusses the quest for strong coupling in FFPs, the fabrication methods, and the wide range of mirror curvatures achievable. The lecture also delves into the applications of FFPs in quantum technologies, such as high-fidelity qubit detection, spin squeezing for atomic clocks, and the creation of entangled states for metrological purposes.