Quantum imaging and sensing is a subject of quantum optics and metrology that investigates the ultimate performance limits of optical imaging and sensing allowed by the laws of quantum mechanics. Using the methods and techniques from quantum optics, quantum imaging addresses the questions of image formation, processing and detection with sensitivity and resolution exceeding the limits of classical imaging. Particularly, the manipulation of quantum entanglement has found enormous potential for improving performances in the techniques of quantum imaging such as quantum interferometry, lithography, microscopy and geometrical optics. Similar improvements have led to new types of high-precision measurement, which can be grouped under quantum sensing or quantum metrology. This book contains new theoretical work on how to utilize the entangled photons produced in a parametric down conversion to improve resolution and sensitivity in quantum interferometry, magnetometry and lithography.