The highly effective and safe mRNA-based severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines draw on decades of painstaking research to overcome the many hurdles for delivering, expressing, and avoiding toxicity of therapeutic mRNA. Cell editor Nicole Neuman talked with Dr. Katalin Karikó and Dr. Drew Weissman, recipients of the 2021 Lasker∼DeBakey Clinical Medical Research Award, to learn more about their quest to develop mRNA-based therapeutics, which led them to the crucial discovery that modification of mRNA could prevent toxicity and increase expression. This conversation has been adapted for print below, with editing for clarity, accuracy, and length.