When the Sefirot are first presented in the Tanya (the classic text from the first Lubavitcher Rebbe) they are called Three Mothers and Seven Doubles. The Three Mothers refer to the three higher Sefirot Keter, Chochmah and Binah (Crown, Wisdom and Understanding). The Seven Doubles refer to the seven lower Sefirot Chesed, Gevurah, Tiferet, Netzach, Hod, Yesod and Malchut (Love, Strength, Beauty, Victory, Majesty, Foundation and Kingship).
However, the original source of the terms Three Mothers and Seven Doubles refer to the Hebrew letters according to Sefer Yetzirah. The three represent Air, Water and Fire; the seven are the letters that come either with a dot inside of them or without the dot.
So in this painting I have the Three Mother letters א מ ש (Aleph, Mem and Shin) as the three higher Sefirot; and the Seven Double letters ב ג ד כ פ ר ת (Bet, Gimel, Dalet, Kaf, Peh, Resh and Tav) as the seven Lower Sefirot.
The Tree of Life and the Hebrew Letters are like the spiritual 'DNA' of the Kosmos. So I painted a Double Helix to hint at DNA - the molecule of Life.
Notice how you can see two three-dimensional cubes in this pictures? One has the letter ד (Dalet) as its center and the other has the letter ר (Resh) as its center. This is like the three-dimensional effect used in my picture The Holy Palace where you can see the center as either going in or out.