The basic principles of x‐ray image formation and interpretation in radiography have remained essentially unchanged since Röntgen first discovered x rays over a hundred years ago. The conventional approach relies on x‐ray absorption as the sole source of contrast and draws exclusively on ray or geometrical optics to describe and interpret image formation. This approach ignores another, potentially more useful source of contrast—phase information. Phase‐sensitive techniques, which can be understood using wave optics rather than ray optics, offer ways to augment or complement standard absorption contrast by incorporating phase information. New approaches that can detect x‐ray phase shifts within soft tissues show promise for clinical and biological applications.