BIOLOGY | MEDICAL | HEALTH on Instagram: "Inside your bloodstream, a microscopic battle is happening every second. A white blood cell — your body’s natural soldier — can detect, track, and hunt harmful bacteria using chemical signals released by the invader. The moment a bacterium enters your body, it leaves behind tiny molecular “footprints.” White blood cells sense these signals and move toward higher concentrations, literally following the scent of the enemy. Once it reaches the bacterium, th