AbstractPulsating stars of different types are in different evolutionary phases, thus allowing one to trace stellar components of different age in the host systems. The light variation caused by the cyclic expansion/contraction of the surface layers makes a pulsating star much easier to identify than constant stars in the same evolutionary phase. Pulsating stars thus offer a powerful tool to disentangle the various stellar generations in systems where stars of different age and metal abundance populate the same regions of the colour-magnitude diagram. An overview is presented of how pulsating stars can be used as tools to study the stellar populations, and the structure and formation process in Local Group galaxies.