Nanocrystals are fundamentally different from the bulk because strain can build up more easily inside the lattice.@footnote 1,4@ Interface from a nanometre-sized crystal to an adjacent material can lead to pattern formation, which can be very dramatic. X-ray diffraction is a generally useful way to measure structure at the atomic level. Recent development of methods exploiting the very high coherence of the latest sources have allowed direct imaging of crystal shapes at lower-than-atomic resolution.@footnote 2@ We have developed a new method to retrieve 3D complex density functions that reveal these strains.@footnote 3@ We will report new results in which interfacial strains between lead nanocrystals and SiO@sub 2@ substrates have been observed. @FootnoteText@ @footnote 1@"Partial Coherence Effects on the Imaging of Small Crystals using Coherent X-ray Diffraction", I. A. Vartanyants and I. K. Robinson, Journal of Physics Condensed Matter 13 10593-611 (2001)@footnote 2@"Three-dimensional Imaging of Microstructure in Gold Nanocrystals", G. J. Williams, M. A. Pfeifer, I. A. Vartanyants and I. K. Robinson, Physical Review Letters 90 175501-1 (2003)@footnote 3@"Three Dimensional X-ray Diffraction Microscopy", Ian Robinson and Jianwei Miao, Materials Science Bulletin 29 177-181 (2004)@footnote 4@"Coherent X-ray Diffraction from Quantum Dots", I. A. Vartaniants, I. K. Robinson, J. Onken, M. A. Pfeifer, G. J. Williams, F. Pfeiffer, T. H. Metzger, Z. Zhong and G. Bauer, Physical Review B 71 245302 (2005) .