Chromatin accessibility refers to the degree to which the tightly packed DNA in chromatin is accessible for transcription factors and other proteins to bind and regulate gene expression. This accessibility is influenced by various factors such as nucleosome positioning, histone modifications, and chromatin remodeling complexes. Research in this area seeks to understand how changes in chromatin accessibility impact gene expression and cellular function, and how these changes can contribute to disease states such as cancer. Techniques such as DNase-seq, ATAC-seq, and ChIP-seq are commonly used to study chromatin accessibility at a genome-wide level.