If a mental health condition deserves to be called "illness of the emotions", that is Bipolar Disorder. Bipolar Disorder is caused by a disturbance of the neurobiological mechanisms that regulate mood, and those who are affected show dramatic and dysfunctional mood swings. This condition affects more than 2% of the general population and is often misdiagnosed with Depression, Schizophrenia or Personality Disorders. Despite the obvious genetic susceptibility, the course of Bipolar Disorder is strongly influenced by environmental factors but liable to a remarkable improvement when appropriate pharmacological treatment and psychoeducational programs are provided. Over the last two decades there have been significant advances in the management of the illness, allowing many people affected to live a normal life. The knowledge of the causes, mechanisms and manifestations of bipolar disorder does not only help to better understand those who directly or indirectly suffer the consequences of the illness, but to identify factors that rule human characteristics such as emotions, feelings and creativity as well.