How galaxies form and evolve across the Universe is one of the greatest outstanding questions in modern astrophysics. Yet this is a topic rife with mystery. To get an insight into galaxy evolution, we have to understand the fundamental process that drives the transformation of baryonic matter in galaxies : star formation. Indeed, young, blue, massive, and very luminous stars drastically affect the spectral energy distribution of galaxies, form heavy elements that enrich the interstellar medium and, due to feedback, inject metals into the intergalactic medium. Understanding how the gas reservoir of galaxies is transformed into stars is therefore pivotal to understanding galaxy formation and evolution. Unfortunately, tracing star formation and constraining star formation laws across the Universe remains a huge challenge. In this talk I will present first an overview of how to trace star formation from the ultraviolet to the far infrared, highlighting some of the recent results obtained through the study of nearby galaxies. In the second part I will explain how these nearby galaxies can be key tools to constrain models of galaxy formation and evolution, and interpret some puzzling high redshift observations.