To meet growing energy demands, sustainable energy solutions require new materials with tunable properties. For example, different materials can absorb different wavelengths of light that can then be converted to energy using solar cells. By using many materials together in a solar cell, a larger portion of light that hits the earth’s surface can be converted to energy. The properties of nanomaterials can be tuned with size, and therefore enable a library of tunable materials to be created using the same parent material. The properties of materials can also be tuned by changes in their composition. Copper sulfide is a unique material because the copper in copper sulfide can readily undergo exchange with a variety of metals to make new compositions, containing three or four elements, that have different properties. By using copper sulfide nanoparticles, we have two different ways to change the material properties, nanoparticle size and nanoparticle composition. However, the ability to finely tune nanoparticle size and composition is still a challenge which requires more research. In NANO-TUNE we used advanced X-ray techniques (mainly Pair Distribution Function Analysis of X-ray total scattering data (PDF)) to study the formation of copper sulfide nanoparticles and to study cation exchange of copper sulfide nanoparticles to different compositions. The objective was to make nanoparticles more reproducibly with increased tunability of their material properties. NANO-TUNE was carried out at the University of Copenhagen and hosted by Professor Kirsten Jensen, a leader in field of PDF.