Tetrahedron: crossing different energy scales

We summarise the content of the talks presented at the Tetrahedron parallel session of N0W2008 with a general overview of the plenary session as introduction to the argument "crossing different energy scales". Neutrino mass and mixing, leptogenesis and CP violation, cosmology hints to neutrino properties, lepton flavour violating processes could enlighten the puzzle of beyond the standard model theories from low to high energy scales. The status of present and future experiments at low and high energies are presented. \ua9 2009 Elsevier B.V. All rights reserved