While originally being used for fluorogenic nucleic acid probes with a stem-loop structure, molecular beacon now refers to a whole family of fluorescence-up probes. This book intends to show a diverse set of instructive examples, from probe design to applications in clinical settings, guided by experts in the field who provide easy-to-follow experiments. The book commences with an introduction to the basic principles of fluorescence, and shows a diverse set of instructive examples, from probe design to applications in clinical settings, molecular beacon technology, the identification of transgenic mice, along with the potential of realtime PCR. This book summarizes all the latest findings and explores powerful techniques designed for geneticist, biotechnologists, molecular and cellular biologists, researchers and developers.