Goosebumps

Goosebumps are small bumps that appear on your skin when your body's tiny muscles, called arrector pili muscles, contract in response to stimuli such as cold, fear, or excitement. This contraction causes the hair follicles to pull hair upright, creating the raised bumps. Evolutionarily, this reaction helped our ancestors appear larger or insulate them with more hair in threatening or cold situations. Today, goosebumps are a normal, involuntary reflex, often triggered by emotional responses or temperature changes, and they typically disappear quickly once the stimulus is gone.