Essential genes are often expressed with high variability during the development of cells. Scientists call this phenomenon "biological noise" and suspect that it is also decisive for the fate of cells, i.e. the developmental pathway a cell takes. Max Planck researcher Dominic Grün now presents a method based on single-cell data to quantify this variability in gene expression. The advantage of the so-called VarID method is that the noise of gene expression can be measured across groups of very similar or related cell states. Thus, the Freiburg researcher hopes to gain a better understanding of the extent to which noise regulates development or is even necessary for the differentiation of cells.