New York University scientists have created what they call "living crystals" in an attempt to study why birds, bacteria, and other living organisms flock together. These crystals are made of hematite colloids — small particles consisting of iron and oxygen floating suspended in a fluid — which constantly group together, split, and return to one another when exposed to blue light. As you can see in the video below, the particles slowly drift apart when the light is turned off.
Even though the study refers to these particles as "living crystals," they're far from alive. As NYU physics professor Paul Chaikin explains to Wired, the crystals only have two of the three characteristics of life — metabolism and mobility — but the particles cannot self-replicate. Instead, the study's value lies in reproducing the principle of flocking in a microscopic, man-made crystal, valuable knowledge which could potentially be used to create materials capable of molecular self-assembly. "I do not think this makes our systems alive, but it stresses the fact that the limit between the two is somewhat arbitrary," Chaikin ponders.