leading in combination with microfocus synchrotron technology and atomic force microscopy to the definition of a new field called nanocrystallography. The few useful examples being shown, concerning yet structurally unsolved proteins, point this very promising approach nanotechnology-based in structural proteomics using highly focused X-rays. This has not to be confused with the important study of nanocrystals, both organic and inorganic, and novel diamond like nanocomposite materials and devices having 3D protein crystals as matrices to be equilibrated with nanoparticles/gold/silver to be utilized in the most diversified electronic applications here also summarized. vii Acknowledgments We are particularly grateful to Giuseppe Zanotti at the University of Padova for his fundamental collaboration during all the crystallographic studies.