We investigate the physics of soft and condensed matter at the micro- and nanometer scale. Soft materials have many peculiar properties that are of fundamental scientific interest and of high relevance for applications. We study the assembly of new materials, and the resulting mechanical and optical properties, governed by equilibrium and nonequilibrium statistical physics. These properties arise from the behavior of many building blocks, which together give rise to new, unexpected mechanical, optical and electronic behavior, giving deep insight into the secrets of condensed matter. The building blocks can be colloidal designer particles, semiconductor nanocrystals (“quantum dots”), or proteins, having applications in foods, biomedicine, and energy materials such as photovoltaics. The insights of our research have implications for condensed matter, materials science, biophysics, photonics and nanoengineering. Examples are crystallization and phase separation, structure and properties of solids and liquids, elastic and plastic properties. The large length and time scales of soft matter allow direct insight into processes that also occur in conventional materials at the atomic scale. Using three-dimensional microscopic imaging and light scattering we bridge length scales from the particle scale to macroscopic.