Figure 50.

Tissue organization includes a tremendous variety of different phenomena. Some show a very high complexity with feedback-loops ranging from the molecular scale up to the multicellular level (a). This includes examples involving complex signaling cascades or gene regulation. Gene regulation, for instance, is able to alter cytoskeletal components, which will affect its network architecture and thereby cellular properties and behavior. At the same time, the resulting interactions on a cellular level or above can involve signaling cascades down to the molecular or genetic level hence forming a multi-scale feedback-loop. In such cases, coarse-graining becomes a very difficult endeavor. Other examples, however, demonstrate nicely that very prominent phenomena on the tissue level can even be described on the cellular scale such as cell sorting in cellular aggregates [542], collective cell migration [536] or epithelial tissue dynamics [554,614].