The primary characteristic that differentiates eukaryotic cells from prokaryotic cells is the cell nucleus. Eukaryotic cells have a nucleus that is surrounded by a membrane, which separates the DNA within from the cytoplasm and other organelles. Prokaryotic cells do not have a true nucleus in that the nucleus is not surrounded by a membrane. Prokaryotic DNA is located in an area of the cytoplasm called the nucleoid region. Prokaryotic cells are typically much smaller and less complex than eukaryotic cells. Examples of eukaryotic organisms include animals, plants, fungi and protists (ex. algae).