Ἀεὶ ὁ θεὸς γεωμετρεῖ

Credited to the greek philosopher Plato it means "Great God is always using geometry" wanting to depict the importance of geometry in the understanding of the cosmos. The phrase is also used as a mnemonic of the irrational number pi (π the ratio of circle's circumference to its diametre) since the number of letters in each word give 3.1415