Roundworms exposed to higher temperatures can exhibit genetic alterations that are passed to offspring through both sperm and eggs, a new study reveals. The changes can endure for up to 14 generations, highlighting the lasting impact that environment can have on organisms. Previous research has found that starvation or exposure to high temperature can alter the expression of messenger RNA in the roundworm, Caenorhabditis elegans, and that this altered expression can persist in up to three generations. Here, Adam Klosin and colleagues exposed a generation of C. elgans to high temperature (25°Celsius), finding that this increased expression of the gene daf-21 in the offspring, but not in their descendants. When C. elgans worms were exposed to the higher temperature for five generations, it took 14 generations for expression of a multi-copy transgene to return to baseline, the authors report. By cross-breeding roundworms, they determined that inheritance of these genetic alterations occurred through both eggs and sperm. Lastly, the researchers found that changes in gene expression they uncovered were driven by a temperature-induced reduction in a particular enzyme, which in turn resulted in several changes that ultimately allow genes to be turned on over many generations as a type of "genetic memory" of high-temperature exposure.