False-colour transmission electron micrograph (TEM) of Chlamydia sp., a genus of small, spherical bacteria which are obligate intra- cellular parasites. This TEM shows the bacteria (red) inside a human cell, with a mitochondrion visible at left (pink oval structure). Chlamydia trachomatis includes strains responsible for the sexually-transmitted disease lymphogranuloma venereum and the eye disease trachoma and inclusion conjunctivitis (TRIC). Presence of C. trachomatis in human genital tract accounts for many cases of non-specific urethritis, which responds to treatment with erythromycin or tetracycline. Magnification: X 11,700 (35mm).