There is considerable consensus that the initial stage of granulation is bacterial adhesion (a physical–chemical process) parallel to the early stage of biofilm formation.

However, treating bacterial adhesion only as a physico–chemical process is limited in explaining all the complex aspects of bacterial adhesion. Bacteria do not have a sharp surface boundary, simple geometry or uniform molecular surface composition. In fact, internal chemi-cal reactions can lead to changes in molecular composi-tion both in the interior and at the surface, and molecules and ions may cross the bacterium/water surface and these processes continue also after adhesion.

Anyway, this physico–chemical approach has value in forming a framework in which biological factors can be added to form a unifying theory of granulation.