Nematode worms. Fluorescent light microscopy footage of one larger and several smaller specimens of the nematode roundworm Caenorhabditis elegans. Fluorescent dyes have been used to highlight the head (green) and internal organs (red). Nematodes are small worms found in a range of environments worldwide. C. elegans is a transparent, soil-dwelling nematode, found in temperate climates. It feeds on bacteria, and reaches lengths of about 1 millimetre. C. elegans is used extensively in biological research. It can reproduce by self-fertilisation (resulting in identical offspring), and takes a short time to reach maturity.