A thorough and accessible biography of Dr. Katalin Karikó, winner of the 2023 Nobel Prize in Physiology or Medicine, whose hard work pioneering mRNA research led to the COVID-19 vaccines. Her monumental contribution to global health care has rightfully placed Karikó as one of the most important scientists in history. She has won awards, given speeches, and appeared in magazines and television programs. But she wasn't always famous—in fact, it took decades for anyone to recognize the importance of her research into RNA and the potential of mRNA to help cells fight off disease. Beginning with her birth in a small village in rural Hungary, Breakthrough tells the story of how a young girl interested in the wildlife around her became an internationally celebrated hero. Exuberant, devoted to her family, and hard-working, Karikó persevered in the face of challenges and obstacles that would have discouraged many of her peers. Her achievements remind us that if we believe in ourselves, no matter the setbacks we encounter, we can succeed.