Kouros (male youth) is the modern term given to those representations of standing male youths which first appear in the archaic period in Greece. This type served certain religious needs and was first proposed for what was previously thought to be depictions of Apollo. The first statues are certainly still and formal. The formality of their stance seems to be related with the Egyptian precedent, but it was accepted for a good reason. The sculptors had a clear idea of what a young man is, and embodied the archaic smile of good manners, the firm and springy step, the balance of the body, dignity, and youthful happiness. When they tried to depict the most abiding qualities of men, it was because men had common roots with the unchanging gods. The adoption of a standard recognizable type for a long time, is probably because nature gives preference in survival of a type which has long be adopted by the climatic conditions, and also due to the general Greek belief that nature expresses itself in ideal forms that can be imagined and represented. These forms expressed immortality. Apollo was the immortal god of ideal balance and order. His shrine in Delphi, that he shared in winter with Dionysius had the inscriptions: γνῶθι σεαυτόν (gnōthi seautón="know thyself") and μηδὲν ἄγαν (mēdén ágan, "nothing in excess"), and ἐγγύα πάρα δ'ἄτη (eggýa pára d'atē, "make a pledge and mischief is nigh").
Who was the immortal god of ideal balance?
Apollo