2C-I is closest, symptomatically, to hallucinogens like psilocybin mushrooms and LSD. MDMA, or ecstasy, also comes up in discussions about it, but mostly because it's derived from the same family, the phenethylamines. (Hallucinations aren't a salient characteristic of MDMA.) It also shows stimulant-like effects, unlike traditional hallucinogens, which are, in some ways, safer--in the sense that a mind-altering compound can be "safe"--because users won't overdose, says Matthew Johnson, a professor of behavioral pharmacology at Johns Hopkins University. Not so with "Smiles."