During interphase, DNA in the cells is present in the form of chromatin; chromatin exists in two primary forms: Euchromatin and Heterochromatin. The latter is the densely packed form of DNA, which is characterised by a paucity of transcription (as mediated by the enzymes RNA Helicase and mRNAsynthase). Indeed, although translation in heterochromatin is limited, its main purposes are thought to include the regulation of gene expression (transcription) and in maintaining the sturctural integrity of DNA. Under the microscope slide, heterochromatin can be distinguished from euchromatin by the fact that the former stains darker. In addition, unlike heterochromatin, euchromatin is only present in eukaryotes, whereas heterochromatin exists in both prokaryotes and eukaryotes.