Periodic behavior is observed in many biological processes: Metabolite concentrations within cells can oscillate, the expression of genes is triggered in waves during the progression through the cell cycle, signaling pathways can show periodic activation. With systems theoretical approaches such as for example bifurcation analysis, we can identify the underlying reasons for this behavior, for example the effect of negative feedback loops. If the mechanistic structure of the system is unknown, we can also analyze oscillations only on the data level. For this we can use decomposition methods such as principal component analysis or Fourier transformations to identify different oscillatory patterns that might also be overlayed. We apply these techniques to the analysis of periodic gene expression in the yeast cell cycle or the measurement of the yeast cell wall rigidity and others