We are at the dawn of a new era of biology where we will start to understand how organisms function together and react or adapt to changes at different molecular levels. This includes the multitude of stresses that organisms are exposed to, from malnutrition and adverse climate events to many other biological, chemical and physical insults. Progress in biological analyses at both a single scale and across scales, have allowed us to further understand organisms in the context of dynamic environments. These can be environments which are changed by disease, commensal cohabitation or competition, as well as abiotic factors. With the molecular understanding we already have at the cellular and organismal levels, and new tools and quantitative approaches, this symposium will address how genotype and the environment bring about phenotypes at the population level.