For more than 50 years, methods for assessing cell viability have been an important research tool in various fields of biology. Cell viability assays can be broadly classified according to the mechanism underlying each assay and how the results are evaluated. This article presents the most used tests to assess cell when planning an experiment are discussed. Particular attention was paid to tests that can be used not only for two-dimensional cellular structures, but also for three-dimensional structures, which have gained wide popularity due to more accurate modeling of biological processes.