I will discuss recent work aimed at describing the statistics of the velocity tensor in turbulence, M_r, coarse grained at a scale r, as a function of r. The work is based on a stochastic model, based on the lagrangian evolution of a set of n-points (the simplest set corresponds to n = 4, a tetrahedron).

I will review Lagrangian concepts for the description of 4 particles and more. The modelling strategy will be discussed, as well as the strategy for obtaining solutions of the model. I will also discuss the implications for energy transfer based on the evolution of lagrangian particles, as well as possible applications to particle-based methods of large-eddy simulations.