Prokaryotic cells do not have a true nucleus. The word "prokaryotic" means "before nucleus." Eukaryotic cells, on the other hand, came after the prokaryotes and contain structures not present in prokaryotic cells.
The only prokaryotic organisms are species of bacteria. Instead of a nucleus, prokaryotes have a region called the nucleoid. This area contains the genetic material of the bacterion in a circular form. Prokaryotes may also contain one or more plasmids, which are circular structures that also contain some genetic material. These plasmids can transfer from one prokaryotic cell to another.
In addition to not having a nucleus, prokaryotic cells also lack other organelles, the membrane-bound structures found in eukaryotes. Organelles include cellular components such as mitochondria, chloroplasts, ribosomes, Golgi bodies and endoplasmic reticuli.