Daniel Liu is a historian of the modern life and physical sciences, whose scholarship explores how ideas of life and matter have moved across different scientific and cultural domains. He has written about how different methods used to study material substances lead to different descriptive languages, visual cultures, and tacit intuitions about how matter behaves — and, by extension, how living matter behaves.

He received his PhD in the history of science, medicine, and technology from the University of Wisconsin-Madison in 2016.. He was previously a Mellon Postdoctoral Fellow in Biohumanities at the University of Illinois at Urbana-Champaign, and an MBL McDonnell Scholar at the Marine Biological Laboratory, Woods Hole. He is currently working with the Cold Spring Harbor Laboratory’s Library & Archives, New York, on a 6-month digital humanities project, ‘Oral Histories of Biology, Medicine, and Pandemic Response’, which examines the history of HIV/AIDS research and activism.

Dan’s most recent article, ‘The Artificial Cell, the Semipermeable Membrane, and the Life That Never Was, 1864–1901’, on the history of the discovery of the cell membrane and the law of dilute solutions, was published in Historical Studies in the Natural Sciences 49.5 (2019), and is available open access at

Seeing Beyond the Limits: Microscopy and Visual Reduction After 1873
Affiliated Project 2020-21

From the Scientific Revolution onward the microscope has been both a practical tool for scientific investigation and working metaphor for the scientific imagination’s access to the microworld. However, in 1873 the German physicists Ernst Abbe (1840–1905) and Hermann Helmholtz (1821–1894) simultaneously discovered that the microscope’s optics are diffraction limited, and that the smallest object a microscope could ever resolve was limited to one-half the wavelength of the imaging light, or about 250 nm under ideal conditions. This is why, for example, a Staphylococcus bacterium at 1 µm across is visible under the microscope, but a coronavirus at 120 nm in diameter is not. While some microscopists sought to stretch the limits and credibility of microscopy through imaginative guesswork and novel microtechnique, others tried to apply a stricter physicalist formalism to understand cells and tissues as colloids with clear, measurable properties.

This project examines the cultural and technical history of scientists’ attempts to overcome this hard, physical limit to visual reduction from the 1873 diffraction limit to today’s super-resolution imaging technologies, and will show how the goal of achieving ever higher optical resolving power was accomplished by harnessing ideas and practices across many disciplines of the natural sciences. It is therefore the aim of this project to explore the dynamics between epistemological reductionism and its historical ties to methodological pluralism in the sciences and their associated visual cultures. Finally, the project will examine how research on formerly-invisible entities like viruses change when the object of study becomes visible. A core case study will be June Almeida’s (1930–2007) discovery of coronaviruses in 1966 through visual methods using the electron microscope.

The (Un-)Bounded Elementary Organism:
Visions of the Continuity of Life in the 'Dark Age' of Physical Chemistry

ICI Project 2018-20

During the first three tumultuous decades of the twentieth century, many important biologists, physicists, and chemists began to think of the living cell not as a bounded object, but rather as a more or less differentiated region of a continuous physical and chemical system. Contrary to intuition, experience, and microscopic vision, this boundary-less state was supposedly a rational explication of thermodynamics and scientific measurement, whereby quantifiable gradients of chemical substances trumped ‘crude’ visual evidence of clear borders. As biologists explored the implications of the physical chemistry of soft matter, some articulated a vision of life that was formally indistinguishable from its non-living milieu. This period, which biochemist Marcel Florkin once called ‘The Dark Age of Biocolloidology’, joins a growing number of scientific movements that science studies scholars have recognized as seeking to dissolve or unsee the boundaries between environments, organisms, and their parts. Besides the currently popular interest in the epigenome, microbiome, and the toxicity of environments, historians of science and science studies scholars have previously found cases of un-bounding in conceptions of immunity, the milieu intérieur, the vital agency of non-human actors, and wild and urbanized ecologies.

As a genre, this kind of barrier-free thinking has been a perpetual underdog, the nonconformist in a sea of more rigid and reductive doctrines. This project pursues two questions: What were the conceptual and instrumental developments that drove this boundary-less, gradated vision of life? Are there cultural or metaphysical reasons why boundaries between organisms and their environments seem more intuitive, despite our theoretical convictions to the contrary? This project will explore the many episodes in the history of ideas when boundaries between a life form and its environment becomes weakened or eliminated entirely—examining their generic similarities, and how they deviate or err from prevailing notions of bodies and milieus.