  The Extra-Cellular-Matrix (ECM) is a complex interconnected 3D network that
provides structural support for the cells and tissues and defines organ
architecture key for their healthy functioning. However, the intimate
mechanisms by which ECM acquire their 3D architecture are still largely
unknown. In this paper, we address this question by means of a 3D individual
based model of interacting fibers able to spontaneously crosslink or unlink to
each other and align at the crosslinks. We show that such systems are able to
spontaneously generate different types of architectures. We provide a thorough
analysis of the emerging structures by an exhaustive parametric analysis and
the use of appropriate visualization tools and quantifiers in 3D. The most
striking result is that the emergence of ordered structures can be fully
explained by a single emerging variable : the proportion of crosslinks in the
network. This simple variable becomes an important putative target to control
and predict the structuring of biological tissues, to suggest possible new
therapeutic strategies to restore tissue functions after disruption, and to
help in the development of collagen-based scaffolds for tissue engineering.
Moreover, the model reveals that the emergence of architecture is a spatially
homogeneous process following a unique evolutionary path, and highlights the
essential role of dynamical crosslinking in tissue structuring.
