An amplicon is a specific fragment or locus of DNA from a target organism (or organisms), generally 200–1000 bp in length, copied millions of times by the polymerase chain reaction (PCR). Amplicons for a single target (i.e., a reaction with a single pair of PCR primers) can be prepared from a mixed population of DNA templates such as HIV particles extracted from a patient’s blood or total bacterial DNA isolated from a medical or an environmental sample. The resulting deep sequencing provides detailed information about the variants at the target locus across the population of different DNA templates. Amplicons produced from many different PCR primers on many different DNA samples can be combined (with the aid of multiplex barcodes) into a single DNA sequencing reaction on an NGS machine.