MM: Human retroviruses are big threats to humans. They evolve to replicate elaborately in human cells using their small genomes. Whenever I find clever mechanisms of retroviruses, they never failed to surprise Correspondence: kjeang@niaid.nih.gov Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, the National Institutes of Health, 9000 Rockville Pike, Bethesda 20892, MD, USA me. At the same time, I feel the challenge to eliminate them from humans and to prevent retroviral diseases. As a retrovirologist, I am fascinated to study these small, but immensely important genomes with their ingenious mechanisms.