Order out of Chaos: the diversity of protists from the perspective of the 21st century. Unicellular eukaryotes, often called protists, remain much less familiar than macroscopic animals or plants, but recent progress in protist biology has revealed that they represent the bulk of the phylogenetic diversity of eukaryotes. Advances in genome sequencing and in methodology of reconstructing phylogenetic relationships from molecular characters have been instrumental in drawing a new consensus of the eukaryotic phylogenetic tree. Although many controversial issues are yet to be sorted out, the best current hypothesis on the eukaryotic tree assumes the existence of five major "kingdoms" called Opisthokonta, Amoebozoa, Excavata, Archaeplastida, and Chromista. While the monophyletic origin of Opisthokonta (including animals and fungi) and Amoebozoa is solidly supported, the remaining three kingdoms are contenious. The notion of the monophyletic Archaeplastida implies that the primary plastid (coming from an endosymbiotic cyanobacterium), evolved only in the common ancestor of green algae and plants, red algae, and an enigmatic algal group called Glaucophyta. The kingdom Chromista is hypothetically derived from a complex creature represented by a host eukaryptic cell bearing a red algal endosymbiont that in some chromists persists to our days as a secondary plastid. One of protist and generally eukaryotic evolurion is an unknown position of the root of the eukaryotic tree. The "unikonts-bikonts" rooting popular in recent years has been eventually shown as groundless, but alternative hypotheses are emerging based on sophisticated analyses of genome sequences.