In less than a decade, our understanding of the Milky Way has largely increased. It is now clear that we live in a disc-like galaxy hosting several stellar structures, namely thin and thick discs, a bar that has developed a B/P, a nuclear disc, and a nuclear stellar cluster, as well as a supermassive black hole at its heart. Such complex system formed in distinct phases. First, gas infall resulted in the formation of the thick disc and stellar halo. The major Gaia Sausage/ Enceladus merger that happened 10—11 Gy ago enhanced star formation in a great way, and contributed to the growth of the thick disc. Finally, the Galaxy entered a quieter era in which the thin disc was formed, eventually giving rise to the stellar bar and nuclear disc. Such scenario matches the broad description of galaxy evolution within a Cold Dark Matter (CDM) Universe... but there are still many loose ends in this Milky Way story.

CDM depicts a Universe dominated by violent processes, mainly major mergers, during the first half of its life. During the second half, secular evolution takes over and fragile structures, like thin discs from which bars and other structures form, are born. New results from JWST are challenging this long-standing picture. The discovery of stellar bars at very high redshift (z>3) implies that cold discs form very early in cosmic history. The transformation of galaxies due to bar-driven secular evolution may thus overlap with the allegedly merger-dominated era, affecting the life of MW ancestors in a way we do not understand yet.

The initial stages of the formation of the Milky Way are also poorly understood. While a pressure- supported remnant, maybe composed of metal-poor stars, is expected to live at the center of Milky Way-like discs, evidence of it has not been found yet. Last but not least, how the currently quiet supermassive black hole affects the evolution of a galaxy like our own throughout its life has been matter of debate for a long time.