What When you look through a microscope, you see a whole new world: Well-known appearances disappear and new objects suddenly emerge. This experience was shared for the first time 350 years ago by a group of naturalists trying to see deeper and deeper into nature. Seeing things through microscopes is not easy, though, and reproducing observations is even harder. My project investigates how early modern microscopists navigated these difficulties through the invention of a variety of representational techniques. These techniques were also used to convey a sense of the scale of sub-visible things. The project shows that the microscopists produced a very sophisticated concept of scaling influential in subsequent attempts to visualise things either too big or too small for the human sense apparatus. Why Today, microscopes are used every day in laboratories all over the globe. The notion that there is another scale somehow underlying all natural phenomena is an ingrained part of our world view. My project reveals how this very particular world view was produced through a historical process involving scientific instruments, collecting practices and visualisation strategies. This gives us a much richer understanding of laboratory science and what this kind of scientific activity is able to create. More than that, the project develops a model for understanding attempts to make invisible things visible. This is highly important today where images of invisible things - be they global climate change, genes or financial markets - carry so much scientific and political weight. How The project will be carried out at the Department of History and Philosophy of Science at the University of Cambridge. Here, I will collaborate with world-leading scholars engaged in producing new histories of science. Using Cambridge as my base, I will travel to nearby archives and libraries, such as the British Library and the Archives of the Royal Society in London, to gain access to letters, diaries, commonplace books and meeting minutes composed by the early microscopists. I will closely inspect the activities of the Royal Society following Antoni van Leeuwenhoek's first observations of 'animalcules', and conduct the first systematic analysis of Nehemiah Grew's representation of scale in his plant-anatomical work conducted for the Royal Society. SSR The success of scientific breakthroughs hinges on scientists' ability to represent visually what cannot be seen with the naked eye. This holds true for disciplines as diverse as molecular biology, particle physics and climate science. To understand these images disconnected from observation, though, gives a misguided conception of what they are able to say. It is one of my aims to show that scientific images, as objective as they may seem, are the products of concrete practice and that they serve very specific ends. By highlighting the specific epistemologies inherent in scientific representations, this project will give us a better understanding of the images of science. This is of high importance in our society as we negotiate how to react to new images of the world.