It is not hyperbole to state that galactic ecosystems have spawned pretty much everything that we hold dear ? including ourselves. These nebular nurseries have incubated all the stars, planetary systems, and many of the complex molecules known to humanity. From there, the myriad of planets in orbit around their hosting stars have further refined the organic matter into even more complex biochemicals. On the surface of one particularly moist planet, life took hold, and evolutionary processes led to you and me collectively pondering the wonders of galactic ecosystems via this book. Given the seminal role of galactic ecosystems in hosting this tale of being and becoming, it is necessary to consider the full sweep of cosmic scales. In this book, we will explore atomic nuclei and their alchemic transmutations within stars, the assembly of atoms into molecules within cryogenic clouds, and prospects for building up the macromolecules necessary for life as we know it. On a much larger scale, we will discover protostars and protoplanetary disks inside molecular cloud cores a few light-years in size, their hosting molecular clouds tens of light-years across, giant molecular clouds and ionized nebulae hundreds of light-years in extent, and finally entire starburst galaxies spanning thousands of light-years. Along the way, we will gain an appreciation for the most massive, powerful, and short-lived stars as they transform their natal environments via their intense radiation, winds, and explosive deaths. Without the elemental beneficence of these stars, rocky planets, water, and life itself would be impossible. Through reading this book, you will obtain a better understanding of your birthright as a ?child of the cosmos.? As with all lifeforms on Earth, and likely myriad of other lifeforms on worlds yet to be explored, this sense of communion pervades the cosmos, made visceral through the awesome creativity of galactic ecosystems.