University Hospital Virgen del Rocio 1 article published in JoVE Genetics Formaldehyde-assisted Isolation of Regulatory Elements to Measure Chromatin Accessibility in Mammalian Cells Alfonso Rodríguez-Gil1, Tabea Riedlinger2, Olesja Ritter2, Vera V. Saul2, M. Lienhard Schmitz2 1Department of Oncohematology and Genetics. Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío, 2Institute of Biochemistry, Medical Faculty, Friedrichstrasse 24, Member of the German Center for Lung Research, Justus-Liebig-University The plasticity of nuclear architecture is controlled by dynamic epigenetic mechanisms including non-coding RNAs, DNA methylation, nucleosome repositioning as well as histone composition and modification. Here we describe a Formaldehyde-Assisted Isolation of Regulatory Elements (FAIRE) protocol which allows the determination of chromatin accessibility in a reproducible, inexpensive, and straightforward manner.