Photometric methods can be applied in a broad range of applications - regardless of whether it is a question of work processes involving cells or microorganisms or whether biomolecules such as nucleic acids and proteins are used. The objectives of photometric analysis can also be different. It is common to determine the concentration of a dissolved substance, but the purity or enzyme activity can also be of interest. Depending on the photometric technique used, there are different measurement methods and various evaluation options. These points are highlighted in the articles in this section.