Nucleosomes are formed by histones, which can post-translationally become modified in more than 100 ways and in addition have many variant forms. The regulatory layers (i.e., dimensions) of chromatin range from single nucleosomes via looping of genomic regions to large-scale folding of whole chromosomes into territories within the nucleus. The accessibility of the chromatin at enhancer and promoter regions determines whether a gene is expressed or not. Furthermore, chromatin architecture imposes which enhancers are able to regulate the expression of which genes. There are various epigenetic methods for the analysis of DNA methylation, transcription factor binding and histone modifications, chromatin accessibility as well as nuclear architecture. Using these approaches, Big Biology projects have already collected a large number of human epigenomes that are publically available.