By Tai-Danae Bradley, Tyler Bryson, and John TerillaMIT Press 2020 CC BY-NC-ND A graduate-level textbook that presents basic topology from the perspective of category theory. Click on the chapter titles to download pdfs of each chapter. Preface 0 Preliminaries 0.1 Basic Topology 0.2 Basic Category Theory 0.2.1 Categories 0.2.2 Functors 0.2.3 Natural Transformations and the Yoneda Lemma 0.3 Basic S