This book fills an important gap in the existing literature by providing a comprehensive discussion of X-ray Phase Contrast Imaging (XPCi) and its various uses and implementations. XPCi could revolutionise all applications of X-ray imaging. It exploits a different mechanism to generate image contrast (refraction/interference instead of absorption), thus enhancing the visibility of all details, allowing the detection of features that are classically considered invisible.XPCi emerged in the mid-1990s, primarily at synchrotron radiation facilities. Initially, its use was considered to be very restricted due to the stringent requirements imposed on the radiation source. New methods which allow XPCi to be used with conventional X-ray sources have recently emerged, thus providing concrete possibilities for transfer into mainstream applications. This has renewed enthusiasm in the field and spawned a large number of new research groups worldwide.This book follows a historical perspective and describes all possible implementations of XPCi. In each case, the underpinning theory is described, the possible experimental realisations are discussed and the targeted applications listed, with specific mentions of the most significant examples. Although sometimes overlooked, X-ray imaging is all-pervasive in our society: medicine, industrial scans, non-destructive testing, security inspections and a vast number of scientific fields rely heavily on it. Hence, the potential impact of XPCi is immense.