This chapter is primarily intended as an introductory text, a pedagogical platform, on the phenomenon ofturbulence in fluids. For the sake of simplicity, the discussion is mostly limited to the case of anincompressible (constant-property) newtonian fluid in simple three-dimensional turbulent flows. Additionalcomplexities related to thermal convection, magnetic forces, nuclear reactions and so forth are ignored onpurpose.The main motivation is to exhibit the general problematic of turbulence in an as simple as possible physicalsetting. Modelling prospecting, which aims at elaborating numerically tractable mathematical models of turbulence,is also brought up.