Plasticity is a fundamental property of the matter, among which the self-folding or the adaptability reflect some laws inherent to the mechanical behaviour of materials, space-time geometry, biochemical processes or morphogenesis at the interface between developmental biology and physics. Contrarily to elasticity, it does not, however, limits itself to it, dressing a high predictive value of the dynamic behaviour of complex systems, what makes it a founding, and not only an emergent or purely systemic property of the matter and the evolution of living systems. Matter-form complexes from which folds are expressions are then defined as aggregates of bound couples directly acting at the anchor of irreducible dimensions or expressions by including the subject in the plasticity of the world.
The geometric analysis of a drawing representing the profile of a man’s head gives us a glimpse of how Leonardo established his constructive approach to profiles from a first form. The geometric analysis of three other Leonardo profiles confirms this approach. It is with this same approach that Leonardo produced his five female portraits.