In this work we present a study of the aggregation and sol-gel transition of colloidal suspensions using a wide range of experimental techniques. We investigate in the first part of this work a model system which undergoes a sol-gel transition in the hope to gain further insight into the fundamental process of gelation. Therefore, a colloidal suspension of nano particles (polystyrene spheres) in water is destabilised to induce aggregation of fractal clusters. The clusters will grow until they finally all connect and form a gel. Combining neutron and light scattering, we are able to measure simultaneously and time resolved the static and dynamic properties of the same sample, which allows us to test well-known theories and to compare our data with recent results of other research groups. Our measurements demonstrate a deviation from classical theories in the critical behavior just before the gel is formed, which we interpret as a glassy cluster phase. The second part of this work describes an experimental setup which is based on a multiple scattering suppression scheme and which allows us to measure even relatively turbid samples faster and with higher precision.