The ability of living matter to rapidly respond to environmental cues, spanning vastly different time and length scales, is a conundrum that has long intrigued biologists and physicists alike. At the scale of a single cell, response is a complex biophysical transduction: from a micro-environmental cue to the phenotypic traits of a cell (for instance, changes in the size, shape or speed in case of a motile cell). In this talk I will focus on one of the key cellular traits – adaptation – and ask how this emerges due to a universal environmental parameter: fluctuations. I will present results from our recent works on motile phytoplankton – one of the most important photosynthetic eukaryotes in oceans – and how, as a deformable colloid, they can rapidly shape-shift in response to hydrodynamic fluctuations resembling ocean-scale turbulence. We uncover that phytoplankton can actively diversify their migration patterns, and that this emergent behavioural trait is underpinned by generation of physiological stress. Intriguingly, the dynamics of stress generation and dissipation are coupled to the structure and duration of the imposed hydrodynamic cues. Our results indicate that fluctuations, even over short time scales, can imprint physiological implications that could last over evolutionary time scales. I will conclude by highlighting why our ability to quantify fluctuation-induced biophysical traits, and corresponding biological functions, are critical in deciphering cellular behaviour, more so during the rapidly shifting patterns that we encounter in our environment today.