Organisms often face new, changing or otherwise challenging environments, which can drive evolutionary adaptations. However, different populations and species often respond differentially to the same environmental change, potentially altering their evolutionary trajectories. For instance, some organisms flourish in new environments, whereas others go extinct. What factors determine individual and population-level responses, and what are the processes and molecular mechanisms that mediate adaptation to new habitats? We are motivated by these broad questions at the forefront of research in ecology and evolutionary biology.