Dopamine molecule keychain (or pendant/earring) in gold.
Dopamine (sometimes abbreviated DA) is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates. Dopamine has many functions in the brain, including important roles in behavior and cognition, voluntary movement, motivation, punishment and reward, inhibition of prolactin production (involved in lactation and sexual gratification), sleep, mood, attention, working memory, and learning. (from Wikipedia; chain not included)
You find his big brother serotonin here: http://shpws.me/q3aI.
Can be used as a pendant on a necklace, keychain, earring, or whatever you find it useful for.