Researchers at UC Berkeley discovered a unique choanoflagellate in Mono Lake, known for its extreme conditions. This microscopic, single-celled organism can form multicellular colonies, similar to animal embryos, and is a sister group to all animals. Remarkably, it harbors its own microbiome, making it the simplest known organism to establish a stable relationship with bacteria. This finding could provide insights into the origins of multicellular life over 650 million years ago.