The Chromista are a eukaryotic supergroup, probably polyphyletic, which may be treated as a separate kingdom or included among the Protista. They include all algae whose chloroplasts contain chlorophylls a and c, as well as various colorless forms that are closely related to them. These are surrounded by four membranes, and are believed to have been acquired from some red alga.
Chromista has been defined in different ways at different times.
It has been described as consisting of three different groups:
History and controversy 
The name Chromista was first introduced by Cavalier-Smith in 1981; the earlier names chromophyte and chromobiont correspond to roughly the same group. Molecular trees have had some difficulty resolving relationships between the different groups. All three may share a common ancestor with the alveolates (see chromalveolates), but there is evidence that suggests that the haptophytes and cryptomonads do not belong together with the heterokonts.
See also 
- Laura Wegener Parfrey, Erika Barbero, Elyse Lasser, Micah Dunthorn, Debashish Bhattacharya, David J Patterson, and Laura A Katz (2006 December). "Evaluating Support for the Current Classification of Eukaryotic Diversity". PLoS Genet. 2 (12): e220. doi:10.1371/journal.pgen.0020220. PMC 1713255. PMID 17194223.
- Cavalier-Smith T, Allsopp MT, Chao EE (November 1994). "Chimeric conundra: are nucleomorphs and chromists monophyletic or polyphyletic?". Proc. Natl. Acad. Sci. U.S.A. 91 (24): 11368–72. doi:10.1073/pnas.91.24.11368. PMC 45232. PMID 7972066.
- Csurös M, Rogozin IB, Koonin EV (May 2008). "Extremely intron-rich genes in the alveolate ancestors inferred with a flexible maximum-likelihood approach". Mol. Biol. Evol. 25 (5): 903–11. doi:10.1093/molbev/msn039. PMID 18296415.
- Cavalier-Smith T (June 2010). "Kingdoms Protozoa and Chromista and the eozoan root of the eukaryotic tree". Biol. Lett. 6 (3): 342–5. doi:10.1098/rsbl.2009.0948. PMC 2880060. PMID 20031978.
- T. Cavalier-Smith (1981). "Eukaryote kingdoms: seven or nine?". Biosystems 14 (3–4): 461–481. doi:10.1016/0303-2647(81)90050-2. PMID 7337818.
- Burki F, Shalchian-Tabrizi K, Minge M, et al (2007). "Phylogenomics Reshuffles the Eukaryotic Supergroups". In Butler, Geraldine. PLoS ONE 2 (8): e790. doi:10.1371/journal.pone.0000790. PMC 1949142. PMID 17726520.