Microbrain is the designation given to the tiny luminous inorganic sapients native to the planet Velara III. They are photo-electric creatures, using cadmium to convert infrared light into electricity, which forms the basis of their metabolism. However, they also require water in the soil to sustain themselves, and presumably other nutrients as well. They can be therefore regarded as more plant-like than animal-like life.
Individually unintelligent, the Microbrains can merge in colonies, becoming progressively smarter. They reproduce asexually and seem to require large amounts of energy for the process. Their chemical composition contains the following substances: silicon, germanium, gallium arsenide, cadmium selenide, sulfide, water, sodium salt and assorted impurities.
Because of the strange nature of the creatures, which in their daily life appear as nothing but microscopic lights shining on the wet sand; the Microbrains' true nature was not recognized by the Federation; which considered Velara III as lifeless and started terraforming procedures on the planet, unknowingly killing the natives. As intelligent creatures, the Microbrains found a way to counter-attack, infecting the terraforming station's equipment and sabotaging it, even killing one of the Federation workers in the process. This led to an investigation by the crew of the USS Enterprise-D, which found out about the Microbrains' existence and attempted first contact diplomacy with them. The Microbrains were skeptical of Captain Picard's claims that the massacre was accidental. They regard humanity as primitive barbarians and describe them biologically as "bags of mostly water" (an insult which Lieutenant Data described as actually accurate). However, they ultimately agreed to stop war if humanity left the planet, not to return until at least three centuries later. Agreeing with the terms, Picard called for a quarantine on Velara III.