Testing is key to controlling the spread of the SARS-CoV-2 virus, but how is it done? This animation from Cold Spring Harbor Laboratory’s DNA Learning Center takes an authoritative look “under the hood” of COVID-19 testing. You will learn about a clever method, polymerase chain reaction (PCR), which amplifies the virus genetic “fingerprint” to detect as few as several virus particles present in a throat swab or other patient sample.