Seton Hall University 1 article published in JoVE Genetics Retrospective MicroRNA Sequencing: Complementary DNA Library Preparation Protocol Using Formalin-fixed Paraffin-embedded RNA Specimens Olivier Loudig1,2,3, Christina Liu1,2, Thomas Rohan3, Iddo Z. Ben-Dov4 1Department of Research, Hackensack University Medical Center, 2Department of Medical Sciences, Seton Hall University, 3Department of Epidemiology and Population Health, Albert Einstein College of Medicine, 4Department of Nephrology and Hypertension, Hadassah - Hebrew University Medical Center Formalin-fixed paraffin-embedded specimens represent a valuable source of molecular biomarkers of human diseases. Here we present a laboratory-based cDNA library preparation protocol, initially designed with fresh frozen RNA, and optimized for the analysis of archived microRNAs from tissues stored up to 35 years.