Evolution of stars from near to far

Many topical questions in astrophysics need an understanding of how stars form, evolve and die. Cepheids and type Ia supernovae are key objects for measuring distances in the Universe. Stars offer a way to measure ages of clusters and starbursts regions in galaxies. They drive the photometric and chemical evolution of galaxies. Through their ejecta in the form of winds and/or at the time of explosive events they inject energy and momentum in their surroundings. Stars are thus cosmic engines driving the evolution of the matter in the Universe. On a smaller scale, characterization of planets requires a very good knowledge of the host star. Is our knowledge of stars already sufficient for addressing all these different questions with some reliability? Unfortunately, the answer is probably no.  During this talk I shall first briefly discuss some challenges in stellar physics. Then I will focus on presenting the physics of rotation in stars of different metallicities. I shall discuss application of rotating and non-rotating (or slowly rotating) stellar models to address then three questions: 1) The evolution of star-planet systems in which the evolution of the star is accounted for through complete stellar models; 2) The evolutionary status of Betelgeuse; 3) The impact of very massive and massive stars on the early chemical evolution of galaxies and on reionisation.