Isotope/Isotopologue ratios have been claimed as
good indicators of planet formation scenarios and
atmospheric evolution. They have been widely studied in
our Solar System, providing information on the planet
formation conditions and the atmospheric compositions that
are currently observed. In contrast, very little is
known about isotope/isotopologue ratios in exoplanets, with
scarce observational studies having been conducted to
date. In this context, during my PhD I developed an
isotopologue-sensitive cross-correlation technique that has leaded to
the detection of molecules in JWST/NIRSpec transmission spectra at
medium spectral resolution, including novel hints of detection of
isotopologues. Studies of isotope/isotopologue ratios in
exoplanets are still in their infancy, but this is
now an emerging field with a lot of potentials
providing an observational constraint on when, where and
how an exoplanet formed in the primordial protoplanetary
disk.