C. elegans, or Caenorhabditis elegans, is a small, transparent roundworm commonly used in scientific research. It is about 1 millimeter long and has a simple body structure, making it an ideal model organism for studying genetics, development, and neurobiology. This nematode has a well-mapped genome and a fixed number of cells, which allows researchers to track cell lineage and study cellular processes. C. elegans is particularly valuable in studies related to aging, behavior, and disease, providing insights that can be relevant to more complex organisms, including humans.