Stimulation is the action of various agents on nerves, muscles, or a sensory end organ, by which activity is evoked; especially, the nervous impulse produced by various agents on nerves, or a sensory end organ, by which the part connected with the nerve is thrown into a state of activity. The word is also often used metaphorically. For example, an interesting or fun activity can be described as “stimulating”, regardless of its physical effects on nerves.