The interaction of atomic or molecular gases with intense femtosecond lasers revealed, since the mid 80's, much unexpected highly non-linear phenomena. One of the most spectacular response of the gas is the emission of coherent light bursts of sub-femtosecond duration, composed of harmonics of the laser frequency over a wide spectrum. I will present and analyze the tomographic imaging of of the molecular wave functions of nitrogen, via a complete set of experimental data consisting of harmonic amplitudes and phases. I will discuss the validity and limitations of the model on which the method is based and demonstrate that, under certain conditions, it allows to image the molecule's HOMO as well as the closest lower orbital (HOMO-1). In addition, combining the spatial and temporal aspects, I will show that the wave-packet of the electronic hole left in the molecule after ionization can be reconstructed with a temporal resolution of ± 300 as.