DNase-Seq is a technique used to study the accessibility of chromatin in the genome. It involves treating cells with DNase I, an enzyme that digests DNA, allowing researchers to identify regions of the genome that are open and accessible for transcription. These accessible regions are often associated with active regulatory elements, such as promoters and enhancers. The resulting fragments of DNA are then sequenced to create a map of accessible regions across the genome. This information helps scientists understand gene regulation and the role of chromatin structure in various biological processes, including development and disease.