Adrenaline molecule necklace.
Epinephrine (also known as adrenaline) is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. Chemically, epinephrine is a catecholamine, a monoamine produced only by the adrenal glands from the amino acids phenylalanine and tyrosine. (from Wikipedia; chain not included)
Can be used as a pendant on a necklace, keychain, earring, or whatever you find it useful for.