“…on different time and length scales, may interact. Therefore, not only do we need to fully investigate processes occurring at a single scale (see, for example [6,40,50,56] and references therein) but we must also determine emergent behaviour from their interactions (see, for example, [1,3,5,10,11,25,42,48,54]). In view of this, it seems that a full understanding of the dynamics of tumour growth requires that traditional (experimental) approaches be accompanied, and guided, by theoretical approaches which can integrate the different physical phenomena.…”