Covid-19 vaccines are starting to roll out in several countries, a momentous breakthrough that hopefully signals a light at the end of this dark pandemic. For Dr. Katalin Karikó, the moment is particularly special. Karikó has spent decades of her career researching the therapeutic possibilities of mRNA, a component of DNA that is considered to be one of the main building blocks of life. Through multiple setbacks, job losses, doubt and a transatlantic move, Karikó stood by her conviction: that mRNA could be used for something truly groundbreaking. Now, that work is the basis of the Covid-19 vaccine.