Confocal scanning laser fluorescence microscopy (CSLM) has been used as a novel and versatile tool to study the interparticle structure of colloidal particles in the bulk of concentrated suspensions. Micrographs showing individual particles were made of a “colloidal glass”, a “colloidal crystal”, and a thermotropic reversible gel. The imaged particles consisted of newly developed monodisperse, fluorescent silica spheres. The fluorophore fluorescein isothiocyanate was chemically incorporated deep inside the l-octadecanolcoated particles. Such model spheres in combination with the improved resolution and optical sectioning of CSLM enable three-dimensional imaging and other measurements that are very difficult with other microscopic techniques or indirect methods like scattering.