New technologies promise to revolutionize the field of molecular ecology. This technological progress comes with its own set of challenges. Among the most important ones is the analysis and interpretation of the data in a way that tells us about the molecular causes of the phenotype of interest and its consequences. In this issue, Whitehead et al. (2010) reveal part of the mechanistic basis of evolved pollution tolerance by studying the developmental and transcriptional response of tolerant and sensitive fish embryos to polychlorinated biphenyls (PCBs), a pollutant commonly found in coastal waters of the United States. By integrating their gene expression profiling data with phenotypic data on individuals along with what is known about pathways by which this pollutant acts in zebrafish and mammals, they are able to suggest detailed mechanisms that have evolved to allow a fish population to adapt to a very damaging pollutant and develop normally.