Tiny robots could soon be delivering life-saving treatments to hard-to-reach parts of the body, according to a new study. Researchers have developed a swarm of tiny'biohybrid' machines measuring a few millionths of a metre long - about the size of a red blood cell. During initial tests, the robots were guided magnetically to sites in the stomach of rats, where they killed cancerous tumours while leaving healthy cells unharmed. The researchers hope the same technique could be used in humans to deliver drugs to remote areas. Researchers have developed a swarm of tiny'biohybrid' machines measuring a few millionths of a metre long - about the size of a red blood cell The team developed the micro-robots by coating a microscopic algae called Spirulina platensis with non-harmful, biocompatible magnetic particles.