In this paper the Authors describe the main functions of microRNAs (miRNAs) along with well acknowledged methods of their detection in biological materials. They include serum, plasma, urine, normal human samples and neoplastic tissues. The Authors also discusses about the relevance of bright field in situ hybridization (ISH) methods for miRNA detection in revealing the cells of origin of specific miRNAs. In particular, the paper highlights the automated ISH protocols for miRNA detection which have recently been proposed. These techniques will enable investigators to further explore the biological role of miRNAs.