Do you remember a well-known phrase, “Men are from Mars, and Women are from Venus?” Do you want to know why you are matched with or have frequent conflicts in important relationships such as marriage, dating, friendship, parent-child relationships, between team members or bosses at work, or even between political leaders? The Planet Phase Type Inventory (or PPPI) has been developed through my decades of scientific studies based on clinical and empirical data and various psychological and psychoanalytic theories on human development and personality. Phase implies developmental phases or changes over time, acknowledging that personality can be dynamic and evolve. Unlike many other personality tests, such as the Big Five (OCEAN), MBTI, or Enneagram, this test is based on a theoretical foundation and some empirical evidence.