Dina Fine Maron, health & science editor at Scientific American, discusses the breakthrough that could help doctors diagnose mental illnesses. Stem cells have enabled researchers to see how lithium affects the brain.

Researchers are converting patients skin cells into brain cells through genetic instruction. This allows them to look at the brain cells of a person with bipolar disorder and better understand how to treat it.

Maron explains this breakthrough will allow doctors to customize a patient's treatment plan, instead of giving them the same treatment given to everyone. Maron says the hope is one day researchers will be able to expose a patient's cells to a particular drug and see how they react before prescribing the drug to an actual patient.