I will make an overview of the classical pulsating variable stars (i.e. SX Phoenicis, RR Lyrae, Anomalous Cepheids, Classical Cepheids) in our Local Group and beyond. I will focus on the evolution and pulsation theory that drives our interpretation of their observed properties in terms of stellar evolutionary tracers and powerful distance indicators. The analysis of low mass (and thus ancient) variable stars can provide sound constraints in our understanding of how galaxies form and evolve. Particular attention will be devoted to the idea of whether the current dwarf spheroidal satellites (dSphs) of the MW are surviving representatives of the Halo protogalactic fragments (Fiorentino et al. 2015). Furthermore, I will discuss the use of classical Cepheids to calibrate SNIa host galaxies with the aim of accurately measure the local Hubble constant, Ho.
I will discuss in detail the possible exploitation of the public variable star catalogues coming from the ESA Gaia mission and the next quantum leap that will be possible in the near future thanks to full sky project with extremely deep limiting magnitude such as the Large Synoptic Survey Telescope. I will conclude describing the importance of resolved stellar population studies in preparing the era for extremely large telescopes.