Understanding mechanical properties of materials requires not only complete determination of the three-dimensional response at a local scale, but also knowledge of the mode or the mechanism by which deformation takes place. Probing mechanical response at such a depth can be only achieved through a diffraction based method. In spite of this, diffraction based methods still are not commonly employed for strain measurements because they are perceived as very time intensive and non-intuitive. Herein we introduce the concept of a diffraction strain ellipsoid, and show how its shape, thickness, and orientation represent the complete deformation state in a powerfully visual and intuitive way. We also show how the geometry of the ellipsoid can be very quickly determined from x-ray diffraction data obtained using a large area detector, and how it can be used to understand micromechanical deformation of nanocrystalline materials.