Heaven, earth and man are the main branches in all major ikebana schools. But it is also a philosophy of balance between the spiritual and the material, and a vision statement for mankind. The "heaven, earth and man" philosophy is a basic component also in Chinese culture and you will find it in Tibetan philosophy as well.
In this video Professor Bira, an 85 year old student of George Roerich, speaks about "heaven, earth and man" in Mongolian thinking, since ancient times depicted as three circles. He gives a modern interpretation naming the principals cosmos, planet and humankind, and explains how this came to be an international symbol of peace and the inspiration for "The Roerich Peace Banner".