To obtain a film from colloidal nanoparticles, the intuitive and common method is naturally to dropcast a concentrated solution of the nanoparticles on the desired substrate or to make a paste of the nanoparticles by adding binders. However, as will be discussed in section 2.2.3, drop casting inherently results in non-uniform distribution of nanoparticles. The preparation of a paste from a nanoparticle colloid also often results in random distribution of the nanoparticles and loss of functionality due to the presence of extra substances. On the other hand, in many applications such as photonic applications, precise nanoscale order of nanoparticles is highly important as the functionalities are strongly dependent on the arrangement. Thus, well-controlled self-assembly techniques as discussed below had to be developed over the years and these techniques are under continuous improvement.