"Tracking the coronavirus’s evolution, letter by letter, is revolutionizing pandemic science."In the beginning, there was one. The first genome for the virus causing a mysterious illness we had not yet named COVID-19 was shared by scientists on January 10, 2020. That single genome alerted the world to the danger of a novel coronavirus. It was the basis of new tests as countries scrambled to find the virus within their own borders. And it became the template for vaccines, the same ones now making their way to millions of people every day. That first coronavirus genome may have been the most important 30,000 letters published in all of 2020.