The proper regulation and spatial organization of heterochromatin is crucial for a broad range of cellular processes, ranging from gene silencing to maintenance of genomic integrity and cell division. The most prominent heterochromatin domains are formed across repetitive sequences (major satellite repeats) around the centromere regions. Those pericentric heterochromatin regions can form clusters in interphase nuclei, termed chromocenters, which are well-discernible as DAPI-dense spots in the nucleus. The localization of chromocenters in the nucleus is not random. In most cell types chromocenters are attached to the nuclear lamina or to nucleoli.