I made a poster version of this picture in the early 1990's which has sold out so I finally reproduced it and made it available as the high quality Giclee print. The red Shin ש and the blue Mem מ boldly show their triangular and rectangular forms - Shin, the 21st Hebrew letter (2+1 = 3 sides of a triangle); Mem, the 13th Hebrew letter (1+3 = 4 sides of a rectangle).
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).
This picture and Kosmic Chambers share an influence from the amazing art of M. C. Escher and are both based on the Sacred Geometry that is expressed in the order of the Twenty-two Hebrew Letters according to Sefer Yetzirah.
This design is also reminiscent of Celtic Knots. Look at the center of this picture and see how inside the central ring are Three Shins in the primary colors - yellow, blue and red (going clockwise from the top). Here, as in my picture Kosmic Chambers, the two outer 'arms' of each Shin is shared with its neighbors.
In this picture you can see the Three Mother Letters of Sefer Yetzirah:
See the large Hebrew letter Aleph א?
Now look at the yellow diagonal line. It can be seen as the Hebrew letter Vav pronounced Wow. It can also be seen as the numeral One. The Wow of this Aleph balances and united the red Shin ש the blue final Mem ם.
The Sefer Yetzirah teaches that of the Twenty-two Hebrew letters, three are primary.
These are the Three Mother Letters - Aleph א, Mem מ and Shin ש.
Shin ש is in the triangle in the lighter red. The sound of Shin is an outward, chaotic, hissing sound. Shin is a vertically oriented letter that is open upward - like Fire that rises to the Heavens. Our orientation to the Heavens is vertical.
This picture can used as a focus for meditation. Sit comfortably and become aware of your chest rising and falling with your breath. Now breathe in through your nose down into your belly with your lips closed. This is the humming sound of the blue letter Mem in the lower part of this picture.