The “fight-or-flight” response characterizes an evolutionary conserved physiological reaction to threat resulting in the prompt secretion of adrenaline by chromaffin cells of the adrenal gland. My research has identified that adrenal glands of different mammal species present variations in cell populations of medulla and cortex, consistently with differences in adrenal physiology and morphology. These differences have confounded the cross-annotation of cells in the organ and mislead relevant transcriptomic analysis. The present project will scrutinize the transcriptional differences in cell populations of the post-natal adrenal gland between different non-human model-species. Determining these differences will provide pivotal information to understand the limitations of using the different animal models, and to elucidate the molecular mechanisms behind the cross-specific differences.