However, as Lau and Ewald would contribute, the diffraction phenomenon is not only explained by reflection. Diffraction is also the result of spherically scattered plane waves that constructively interfere at certain angles from incidence (Fig 1a). This diffraction condition is visualized as the "Ewald sphere" constructed in reciprocal space, where points represent the spatial frequency of lattice planes. The diffraction condition is when the path difference of incoming (𝑘 ) and diffracted (𝑘) X-ray wavevectors is equal to an integer number of wavelengths (𝜆):