Nitrogen isotopes in the interstellar medium: A chemical journey across the Galaxy

One of the most important tools to investigate the chemical history of our Galaxy and our own Solar System is to measure the isotopic fractionation of chemical elements. This is the process that distributes the less abundant stable isotopes of an element in different molecules. The isotopic ratios are governed by two main processes: 1. chemical evolution of the whole Galaxy due to stellar nucleosynthesis; 2. local fractionation effects. In this Proceeding we report some results highlighting both processes towards massive star-forming regions