Many people are unaware that in their chest, between the upper tips of the lungs, there is a small gland similar to to the thyme flower: the thymus, just 30 grams. White blood cells—the human body's defenses—are formed inside the bones, but some travel to the thymus to mature and become cytotoxic T lymphocytes, real killers in the immune system, capable of even destroying cancer cells. A team headed by the Spanish biochemist Miguel Reina has now discovered a way to strengthen these soldiers and improve immunity against tumors and infections. Their discovery is published this Wednesday in the magazine Nature, vanguard of the best science on the planet.