Here’s a tip I always keep in mind when thinking about viruses: I like to break down their structure into three main parts—the genetic material, the protein coat, and sometimes a lipid envelope. The genetic material (either DNA or RNA) is like the instruction manual for making more viruses. That’s wrapped in a protective protein shell called the capsid. Some viruses also have an outer envelope made of lipids, which they steal from host cells. Keeping this simple framework helps me quickly recall how viruses are built and how they function.