It is truly remarkable how closely the largest structures of the Universe are interwoven with the tiniest, the elementary particles. In this book, we have explored the smallest and, as far as we know, most fundamental building blocks of Nature. From the very first chapter, we outlined how elementary particles gradually combine into more complex structures, forming nuclei, atoms and molecules on ever larger scales. The appearance and governing laws of the resulting structures at first often have no apparent connection to the laws of the underlying elementary particles. The journey from the smallest to the largest scales is not merely one of increasing distance, but rather a return to a common origin. In this final chapter of the book, we complete this circle by examining some examples of the deep connection between cosmological observations and discoveries in particle physics.