Microfossils through Time: An Introduction is the first textbook of micropaleontology addressing undergraduate students. It presents an introduction to each group of microfossils, from bacteria to microscopical debris of vertebrates, demonstrating the broad range of study of this subdiscipline of paleontology. Not only those groups of microscopic fossils, which are traditionally considered relevant to micropaleontology, are presented (e.g., dinoflagellates, charophytes, radiolarians, spores and pollen, ostracods, chitinozoans, etc), but also others that often occur in micropaleontological samples (e.g., bivalves, echinoderms, fish debris, mammalian teeth, etc). Each of the more than forty microfossil groups are presented in an order that follows the paleontological classification, with a history of study and a variety of data on morphology, living habitats, stratigraphical distribution and their evolution, as inferred from the fossil record. The text is intended as the starting point for a new generation of textbooks that presents micropaleontology in a new structure capable of assuring an efficient transfer of expertise to the younger generations of scientists. This book will help those making their first steps in micropaleontology to develop defensible models of what microfossils are, laying the foundations for fundamental and applied studies. It introduces micropaleontology as a tool for conducting applied studies in biostratigraphy, paleoecology and for paleobathymetric estimates, basin analysis and reconstructing geological history, or related to sequence stratigraphy. It also addresses students and specialists in biology and genetics, offering a solid data base to be integrated with the other two principal components of the triad of sciences that studies the evolution of life on Earth.