Tracking how cells move around the body is key to preventing diseases, like cancer, from spreading.
Most people know illnesses like intestinal upsets can be caused by bacteria. They don't link bacteria with an illness like multiple sclerosis.
Is it possible to be too clean? Scientists are investigating the "hygiene hypothesis".
When immune cells detect an infectious organism, they produce fever-making chemicals. These chemicals prompt the body to produce prostaglandins, which turn up the thermostat in the brain.