Crystals are solid bodies whose atoms, molecules or ions have a periodic spatial structure. Analogously to spatial structure, their elements are arranged periodically in a spatial pattern or lattice. In accordance with Steno's Law (or law of constancy of interfacial angles), "the angles between two corresponding faces on the crystals of any chemical or mineral species are constant and characteristic of this species"; regardless of size, occurrence, or whether they are natural or man-made.

The characteristic feature of crystals in their ideal form is their polyhedral shape.

The principles for filling a defined space are: tight packing, a high degree of symmetry, plus the maximum possible relation and adjacency to other elements.

The discovery of X-ray diffraction by Max von Laue in 1912 was decisive in the development of crystallography, as it demonstrated both the lattice structure of crystals as well as the wavelike nature of X-rays.

The structure of crystals can be described geometrically. Their symmetric axes of rotation are digonal, trigonal and hexagonal. Pentagonal rotational axes and those with numerical factors greater than six do not occur with crystals, because it is not possible to fill a surface with equal-sided polygons having a greater number of sides.

Bravais has listed seven systems containing all possible crystal forms.

I suspect that all crystal systems are contained in the intracubic part of the Metaeder and its length or angular distorsions.

However, final proof that the complete and final list of all possibilities of crystalline figurations are contained in the Metaeder remains to be produced by further studies.

In conclusion, spatial structure in building is analogous to crystal structure enlarged by approximately billion times.

CRYSTALS IN THE METAEDER
NEURAMINIDASE CRYSTALS AS RHOMBIC DODECAHEDRONS
ROCK CRYSTAL
PYRITE
SNOW CRYSTALS
SYMMETRICAL AXES OF CRYSTALS
STRUCTURE OF THE DIAMOND
THE CRYSTAL AS A HEXAGONAL PRISM
ROCK CRYSTAL
DOUBLE SPAR
"TRIKLINE" ARCHITECTURE LAMING/TULOUP
SNOW CRYSTAL