False-colour transmission electron micrograph (TEM) of the bacterium Mycobacterium tuberculosis, the causative agent of tuberculosis in humans. This bacterium forms filamentous, branching structures which are inhaled into the lungs to form a primary tubercule, an initial focus of infection; spreading takes place via adjacent lymph nodes. This form is called pulmonary tuberculosis (or consumption). Many people are infected without showing symptoms, whilst the body's immune system holds the disease in check. They remain carriers, transmitting the disease by coughing or sneezing. Magnification x 5700 at 6x7cm size.