From public reminders to sanitize drinking water to philosophical speculation on the sublime, this study documents how microscopical science appears in a wide range of cultural and intellectual concerns. Interweaving a genealogy of microscopy with readings of literary texts, I show how the microscope embodies certain epistemological formulations that disclose original literary and philosophical networks. Through readings of Ralph Waldo Emerson, Charles Sanders Peirce, Herman Melville, and Emily Dickinson, along with diverse intertexts from philosophy, science, and literature, I expose the influence that microscopy had on nineteenth century American metaphysics, spirituality, fiction, and figuration. It explores, for example, questions of invisibility and faith in early American writers such as John Winthrop, Jr. and Cotton Mather, who believed that the microscope presented a divinely mandated opportunity to fully comprehend God's universe, and follows through with Emerson's later arguments that the instrument endorses a dangerous mechanistic ideology at odds with his spiritual sensibilities. It explains how Peirce viewed the microscope as a means through which to rescue philosophy from crude and untenable metaphysics, how Melville embraced the microscopical to enact a theory of symbolism, how Dickinson meditated on the spiritual dangers of "looking too closely," and how writers from numerous disciplines have all struggled to make sense of extended human vision. The study closes by discussing the model of "deep time" literary history, and questioning the status of the aesthetic detail when placed on the vast scale of a universe expanded by optical instruments. This cosmic vastness threatens to annihilate the significance of human intellectual pursuits, leading to a "scaling-up" that I argue is best addressed in existentialist terms. The microscope made available a novel means of imagining the infinite while revealing the limits of natural perception, expanding assumed scales of understanding, and challenging inherently prejudiced biological categories and social stratifications. This work demonstrates how the microscope came to be, the polemics it provoked, the ideas it preserves, and the role it played in the formations of nineteenth century philosophy, science, fiction, and poetry.