  Recent studies have revealed that the Multiple Populations (MPs) phenomenon
does not occur only in ancient and massive Galactic globular clusters (GCs),
but it is also observed in external galaxies, where GCs sample a wide age range
with respect to the Milky Way. However, for a long time, it was unclear whether
we were looking at the same phenomenon in different environments or not. The
first evidence that the MPs phenomenon is the same regardless of cluster age
and host galaxy came out recently when an intermediate-age cluster from the
Small Magellanic Cloud, Lindsay 1, and a Galactic GC have been directly
compared. By complementing those data with new images from the Hubble Space
Telescope (HST), we extend the comparison to two clusters of different ages:
NGC 2121 ($\sim$2.5Gyr) and NGC 1783 ($\sim$1.5Gyr), from the Large Magellanic
Cloud. We find a clear correlation between the RGB width in the pseudo-colour
$C_{F275W,F343N,F438W}$ and the age of the cluster itself, with the older
cluster having larger $\sigma(C_{F275W,F343N,F438W})^{RGB}$ and vice-versa.
Unfortunately, the $\sigma$ values cannot be directly linked to the N-abundance
variations within the clusters before properly taking account the effect of the
first dredge-up. Such HST data also allow us to explore whether multiple
star-formation episodes occurred within NGC 2121. The two populations are
indistinguishable, with an age difference of only 6$\pm$12 Myr and an initial
Helium spread of 0.02 or lower. This confirms our previous results, putting
serious constraints on any model proposed to explain the origin of the chemical
anomalies in GCs.

Solar and Stellar Astrophysics;Astrophysics of Galaxies