Neisseria meningitidis, also called meningococcus, is a bacterium responsible for meningitis and septicemia. Its most serious form, purpura fulminans, is often fatal. This bacterium, which is naturally present in humans in the nasopharynx, is pathogenic if it reaches the blood stream. Scientists have deciphered the molecular events through which meningococci target blood vessels and colonize them. This work opens a path to new therapeutic perspectives for treating vascular problems caused by this type of invasive infection.