In the current Corona pandemic, the SARS CoV-2 virus is killing a great many people and restricting life around the globe. But viruses also have good sides that we can use. According to the common definition, viruses do not belong to living organisms. Nevertheless, they have a great influence on evolution and are even a part of us humans. Some virus building blocks have anchored themselves in our genome and reproduce with us. They help us survive. Viruses built into the human genome - known as endogenous retroviruses - contribute to the formation of the placenta, for example. Other viruses attack bacteria, preventing them from spreading and thus creating space for further life. At the Bernhard Nocht Institute in Hamburg, viruses are studied, catalogued and archived. Bird flu, Zika, Ebola - a total of several thousand viruses have been completely sequenced, and the actual number is probably many times higher.