Alveolates are a diverse group of single-celled organisms that belong to the domain Eukaryota. They are characterized by the presence of small cavities, or alveoli, beneath their cell membranes. This group includes well-known organisms such as dinoflagellates, apicomplexans, and ciliates, which play important roles in marine ecosystems and human health. Alveolates can be found in various environments, from oceans to freshwater and even in soil. Some species, like dinoflagellates, are known for their bioluminescence and can cause harmful algal blooms, while others, such as apicomplexans, include parasites that can infect humans and animals, like Plasmodium, the causative agent of malaria.