Next to the brittle rock structure as discussed in previous chapter, there is a ductile rock structure. Deformation of such rock structures involves so-called creep mechanisms. Different creep mechanisms result in different physical flow regimes. The various creep mechanisms are therefore outlined in this chapter. The interaction of the various types of crystal motions in the rock, which results in creep, gives rise to global macroscopic flow. The question of how this flow exactly is accomodated starts this chapter. After that so-called steady state foliation is clarified and moreover the different creep mechanisms are outlined. The chapter ends with the explanation of creep tests and the use of the inferred deformation maps.