This document provides a classification of viruses based on their nucleic acid composition and structure. It divides viruses into DNA viruses and RNA viruses, and further classifies them based on whether their genome is single-stranded (SS) or double-stranded (DS). Some of the major virus families described for each category include Geminiviridae, Nanoviridae, Reoviridae, Closteroviridae, Potyviridae, and Tombusviridae. Retroviruses are also discussed, noting they contain reverse transcriptase and are divided into single-stranded RNA and double-stranded DNA families like Caulimoviridae.