Blood. A cosmos of cells. The restless ones: red blood cells. The guardians: multilobed neutrophils that mount the first phases of the immune response. The healers: tiny platelets—once-dismissed as fragmentary nonsense—that redefined how we respond to breaches in the body. The defenders, the discerners: B cells that make antibody missiles; T cells, door-to-door wanderers that can detect even the whiff of an invader, including, possibly, cancer.
