In a recent publication in Science, the Olson Lab used chemical and molecular tools to elucidate the mechanism of psychedelic-induced neuroplasticity. They found that activation of intracellular 5-HT2A receptors was essential for psychedelics to promote cortical neuron growth. Unlike psychedelics, serotonin is too polar to passively diffuse across cell membranes, and thus, it does not produce the same effects on structural neuroplasticity.