The nucleoid (meaning nucleus-like)'s an irregularly-shaped region within the cell of prokaryotes which has nuclear material without a nuclear membrane and where the genetic material's localized. The genome of prokaryotic organisms generally's a circular, double-stranded piece of DNA, of which multiple copies may exist at any time. The length of a genome widely varies, but generally's at least a few million base pairs. Storage of the genome within a nucleoid can be contrasted against that within… (More on Nucleoid)