The interaction between experimental physics and theory is rather complex, but when in gear they can open up entire research fields. I will discuss two opposite cases of scientific work where theory and experiment were interacting and showing that scientific coherence can emerge from these duals works. In the first case, the experiment was performed as a verification of a complex ab-initio modelization. Indeed, time resolved electron diffraction was used to investigate the complex electron lattice interactions in metals and compared the extracted values to the ab-initio calculations. In the second case, simulation was used to support an experimental result. We recently demonstrate the occurrence of self-amplification in prototypical molecular materials upon photo-excitation. Thanks to a recently developed Monte-Carlo model solving mechano-elastic interactions, the main experimental result was reproduced leading to the clear identification of the main parameters at play.