Points of Interest in a Design Grid (First, Second, Third, and Fourth)
In the book The Art of Composition: A Simple Application of Dynamic Symmetry, Michel Jacobs describes the eyes of a Dynamic Symmetry grid as "points of interest." For example, within the basic armature of the rectangle, regardless of the size of the root, you would have four "points of interest"- one point for each two intersecting diagonal lines. However, which point (out of the four eyes) that becomes the principle, secondary, etc. is entirely up to the artist.
One important concept that all beginners should be aware of when discussing the "points of interest" in a Dynamic Symmetry design is that it's not always necessary to have your principal point of interest fall precisely on one of the four eyes. Because master artists subdivide their rectangles, often going down multiple levels, their principle point of interest might not land on any one of these intersecting points on the first level in a design scheme.
In the painting below, from the book Colour in Portrait Painting, notice how Michel Jacobs is only using one point of interest in the root 2 Dynamic Symmetry rectangle. However, when you continue to break down each root 2 within the mother rectangle, you can see how other elements of the portrait fall into place. For example, notice how the eyes of the man fall precisely center on one of the smaller root 2 rectangles. Additionally, if you were to break down the root 2 rectangles on the top left-hand side of the composition, you would see how the picture hanging on the wall also falls on divisions of the root 2 Dynamic Symmetry rectangle.