(RGBs) and MSs, which comprise a population, A, of stars with primordial helium abundance (Y$\sim$0.246) and two stellar populations, B and C, enhanced in helium by $\Delta$Y$\sim$0.01 and 0.03, respectively (Milone et al.2010, 2013, 2018; Dotter et al.2015). Spectroscopy shows that population-C stars are enhanced in N, Al, Si, and Na and depleted in C, O, and Mg, with respect to the population A, while population-B stars have intermediate chemical composition (e.g.Grundahl et al.2002; Yong et al.2003, 2005, 2013, 2015; Carretta et al.2009, 2012, see Table 2 from Milone et al.2013 for the average chemical composition of the stars in the three stellar populations of NGC6752). Multi-band [*HST*]{} photometry suggests possible star-to-star helium variations among population-A stars (Milone et al.2017b, 2018).

While multiple populations of NGC6752 are widely studied along the RGB and the upper MS, the M-dwarf regime is almost unexplored. The only available information on stellar populations among low-mass stars is provided by Dotter et al.(2015), who show that the F110W$-$F160W color distribution of NGC6752 stars, estimated $\sim$1.5 F160W magnitudes below the MS knee, is much larger than that expected from a simple population.

The exquisite photometry from the [*HST*]{} large program on NGC6752 allowed us to identify 