As was explained in the preceding chapter the sol-gel process involves a complex pattern of chemical reactions that proceed simultaneously. This allows chemical modification in all stages of the process for the optimisation of the structure of the attained silicates to fit a particular application. These modifications can have their effect at the molecular, but also on the mesoscopic and macroscopic level and may include variation of the silicate precursor and the reaction conditions, as well as post treatment of the resulting gels and glasses.