Studying single mRNA molecules has added new dimensions to our understanding of gene expression and the life cycle of mRNA in cells. Advances in microscopes and detection technology have opened access to single molecule research to most researchers interested in molecular biology. Here we provide an overview technique for single molecule studies of RNA in either fixed samples or in living cells. As part of a volume on mRNA turnover, it is increasingly relevant, because many of the recent advances in studies of mRNA turnover have suggested that there is non-homogeneous distribution of turnover factors in the cell. For this reason, understanding of spatial relationships between mRNA and mRNA turnover factors should enrich our understanding of this process.