The Universe still holds profound mysteries: How did it begin, how did the first stars and galaxies form, and how did the extraordinary diversity we see today emerge from the early cosmos? To answer these questions, astronomers build ever larger telescopes, reaching farther and deeper into space and time.

When we look up at the night sky, we see beauty—but we are also looking at a vast cosmic archive. The light reaching our eyes may have travelled for thousands or millions of years, carrying with it a message from a distant time and place.

In this talk, we will explore one way in which astronomers read this hidden history: through the chemistry of stars. Stars are cosmic factories in which many of the elements of the periodic table are produced. Through nuclear reactions in their interiors, and through processes associated with stellar deaths and explosions, stars create and redistribute elements throughout space. Every star is part of a much longer story, born from material enriched by earlier generations of stars and eventually returning newly created elements to space. By measuring the abundances of these elements, astronomers can reconstruct the chemical evolution of galaxies. Through the study of nucleosynthesis—the processes by which elements are forged inside stars and in stellar explosions—we can follow the gradual chemical enrichment of galaxies.

Here, we will focus on our own Milky Way and on its satellite galaxies, our best laboratories in which we can investigate how stars, gas, and elements have evolved over cosmic time.