Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Curs: 2018, Tutor: Josep TaronA study on the Leggett-Garg inequalities, which determine if the classical hypothesis of macroscopic realism is true for observables at atomic and sub-atomic scale measured at different times. It is found that the bounds in the Leggett-Garg inequalities calculated under classical assumptions are violated when recalculating the Leggett-Garg inequalities under quantum mechanical assumptions. Finally, with the help of the results of an experiment based on neutrino flavour oscillations, it is found that classical assumptions are wrong.