Aeukaryote is an organism with complex cells, or a single cell with a complex structures. in these cells the genetic material is organized into chromosomes in the cell nucleus. animals, plants, algae and fungi are all eukaryotes. there are also eukaryotes amongst single-celled protists. unlike unicellular archaea and bacteria, eukaryotes may also be multicellular and include organisms consisting of many cell types forming different kinds of tissue. prokaryotes are singled cell organisms.