Disruptive mood dysregulation disorder (DMDD) is a condition defined by frequent explosive outbursts occurring within the context of chronic, pervasive irritability, beginning in early childhood. This lecture reviews how the condition evolved and speculates that although it originated ostensibly as a response to the overdiagnosis of bipolar disorder in children, and the overdiagnosis of bipolar disorder occurred because of the absence of a good diagnostic home for explosive outbursts. Evidence suggests depression and anxiety are outcomes of DMDD however that does not account for the outcome of the outbursts. I will also discuss briefly the relationship of other mood and behavior disorders to DMDD, assessment and treatment.