In this talk, I will present our recent efforts in probing the physical processes underlying self-assembly of colloidal gels and crystals. Nano-meter to micron sized particles in suspension can be a powerful platform for assembly novel functional materials, but the challenge is to design interactions such that desired functionality is achieved. Moreover, for practical purposes this must be done on a large scale. First, I will discuss our work on using particles with many mobile binding sites, where particles can ‘choose’ their number of neighbors by assembling adhesion patches between particles. Second, I will discuss nucleation and growth of crystals formed from pairs of charged colloidal particles in suspension.