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Two broad scenarios have been suggested for the long-held problem of the formation of multiple populations (MPs) in Globular Clusters (GCs). According to the first option comma GCs have experienced multiple star-formation episodes and provided a major contribution to the mass of the Galactic halo. As the alternative comma there was a single star-formation episode comma but a fraction of stars has successively accreted material processed and ejected by massive stars of the same generation. The mass functions (MFs) and the chemical composition of very-low mass M-dwarfs are the missing observational constraints to disentangle between the two scenarios. Historically comma MPs in the GCs have been mostly investigated from UV and visual filters that are very sensitive to the bizarre chemical composition of the GC stars more massive than virgul0.6 solar masses. Due to the observational limits of the UV detectors comma the faintest region of the color-magnitude diagram (CMD) is nearly unexplored. In the era of JWST comma blind to the UV comma the recent discovery comma based on NIR HST photometry comma of multiple sequences of very-low mass stars has provided a new window to study MPs. We propose to combine F110W and F160W photometry comma which allows us to investigate the MPs phenomenon in the poorly-explored M-dwarf regime comma with F275W comma F336W comma and F438W data comma mandatory to explore the brightest region of the CMD. From the synergy of NIR comma optical and UV photometry we will constrain the chemical composition of the MPs and derive for the first time their mass-functions in the interval between virgul0.1 and 0.8 solar masses. Our results will provide a major step forward to constrain the formation scenarios of MPs