Serotonin is implicated in functions as important as humour, sadness, feelings of aggression, anxiety and sleep disturbances, among others. A deficiency in serotonin release has been related with schizophrenia, depression, bipolar disorder, obsessive-compulsive disorders, chronic pain and eating disorders. All of this supports how important it is for the central nervous system to function well. Now, to facilitate “in-vitro” studies of the neurons that produce this substance, a technique has been developed that enables them to be obtained from human pluripotent cells, both embryonic and human iPS cells (Nature Biotechnology 34; 89-94, 2016). The use of human embryonic stem cells has objective ethical difficulties, but not so human iPS cells, so their use opens up a scientific and ethical avenue for the production this substance from neurons, and to take another step forward in the treatment of conditions linked to serotonin imbalance.