Welcome to the Algae World!  Specifically, the world of microscopic algae. Algae are not a taxonomic group, but rather a disparate group of organisms that all have chlorophyll a, have single-celled gamete-forming cells, with water-dispersed spores and includes their colorless relatives. They occur in marine, estuarine and freshwater environments, may occur in the soil or on snow, and some live in hot springs or in (!) ice. Some groups, such as the Cyanobacteria, have been around for 2-3 billion years and others are close allies of land plants. Collectively, algae contribute more oxygen to our environment than all of the rainforests combined. They are the base of the foodchain in almost all aquatic ecosystems. They are involved in global cycling of carbon, oxygen, nitrogen and silica. Some algae can produce toxins that can cause die offs of vertebrates and inflict tens of millions of dollars of economic impact. Other are being used as sources of food, nutricueticals, biofuels, building materials and provide compounds that are used as medicines.