We study how animals modify their phenotypes in response to environmental cues through phenotypic flexibility and developmental plasticity. When animals encounter environment that is new or outside of the norm, the balance between animal’s phenotype and surrounding environment is disrupted. In response, animals modify their physiology and behavior to best match the environment, often through activating the hypothalamic-pituitary-adrenal axis. If this phenotypic plasticity takes place in parents, it may serve as a forecast of future environment for developing animals through maternal effects. Early-life environments provided by parents or influenced by other factors may directly cause irreversible phenotypic change in young animals. My lab studies both transient and permanent effects of an environment on endocrine, immune, and nervous systems to understand the basis of inter-individual variation in organismal responses to stressors and how it relates to performances of the individuals.