Opium poppy (Papaver somniferum) flowers and seed heads in a field. This poppy is the source of opium, a narcotic resin that contains the alkaloids morphine and codeine. These are used by the pharmaceutical industry as painkillers (analgesics). Opium can be refined to yield pure heroin, an illegal drug that induces feelings of warmth and euphoria. Frequent use leads to an increase in tolerance and addiction.