Living cells are non-equilibrium, fluctuating entities that react to environmental cues and must make reliable decisions. Fluctuations manifest themselves in cellular heterogeneity in gene expression, even when cells have the same genome. To study when this heterogeneity may be advantageous or detrimental and shed light on the underlying fundamental biological processes and their dynamics, we use an interdisciplinary approach that combines a variety of experimental, computational and statistical techniques, probing biological model systems and genetic circuits at various scales. To make progress we encourage lively interactions between students of different backgrounds.