Chromalveolata was proposed to represent the organisms descended from a single secondary endosymbiosis involving a red alga and a bikont.

Thus, two papers published in 2008 have phylogenetic trees in which the chromalveolates are split up,[5][6] and recent studies continue to support this view.

[9] In 2005, in a classification reflecting the consensus at the time, the Chromalveolata were regarded as one of the six major clades of eukaryotes.

Each major subgroup has certain unique features, including the alveoli of the Alveolata, the haptonema of the Haptophyta, the ejectisome of the Cryptophyta, and the two different flagella of the Heterokontophyta.

Dinoflagellates produce red tides, which can devastate fish populations and intoxicate oyster harvests.

Brown algae, most specifically kelps, create underwater "forest" habitats for many marine creatures, and provide a large portion of the diet of coastal communities.

The siliceous shells of diatoms have many uses, such as in reflective paint, in toothpaste, or as a filter, in what is known as diatomaceous earth.