Rosin is a sticky, amber-colored substance that comes from the sap of pine trees and other conifers. When tree sap is heated and processed, the liquid part evaporates, leaving behind hard, glassy rosin. If you've ever touched pine sap and felt how tacky it is, rosin has that same sticky quality.

Musicians use rosin in a fascinating way. Violinists, cellists, and other string players rub rosin on their bows to create just the right amount of friction against the strings. Without rosin, the bow would slide smoothly across the strings without making much sound. With rosin, the bow grips and releases the string rapidly, producing that rich, singing tone. Too little rosin and the sound becomes wispy; too much and it can sound scratchy.

Baseball pitchers also use rosin to improve their grip on the ball, especially on humid days when their hands get sweaty. Gymnasts and rock climbers use powdered rosin on their hands for better grip. Ballet dancers even apply rosin to their shoes to prevent slipping on smooth stages.