Philip Nelson’s book From Photon to Neuron: Light, Imaging, Vision completes a trilogy begun by Biological Physics (2004) and Physical Models of Living Systems (2015). Those works establish Nelson as the preeminent author of textbooks at the intersection of physics and biology. All three books are aimed at upper-level undergraduates who already have studied a year of physics and calculus, but the texts are rich enough for the graduate level too.

From Photon to Neuron covers topics throughout biological physics. For instance, fluorescence microscopy is a theme Nelson introduces early and revisits often. He devotes one chapter to color vision and another to superresolution microscopy. My favorite chapter, “Imaging by X-Ray Diffraction,” begins with Rosalind Franklin’s iconic x-ray diffraction pattern of DNA and then develops enough theory to explain how James Watson and Francis Crick could, at a glance, obtain the key information they needed to derive their famous double helix structure.

Nelson presents enough electrophysiology to describe how rhodopsin’s absorption of a photon causes a voltage signal across the neural membrane and enough physical optics to explain the iridescence of butterfly wings. The network diagrams of signaling cascades are a little dry, but that may reflect my own tastes rather than Nelson’s presentation. Other topics include photosynthesis, fluorescence resonance energy transfer (FRET), and two-photon imaging. David Goodsell’s beautiful drawings (right) further enhance the material.

Instructors considering From Photon to Neuron may wonder if it is best suited for physicists interested in biology or biologists interested in physics. In my opinion, physics students will gain the most from this book, as they should be able to handle most of the mathematics. Biology majors will be challenged—Nelson includes, for example, the Fresnel integral—but the book will improve their quantitative skills. Instructors should also be aware that part 3 contains some advanced topics, such as the quantum mechanical analysis of the harmonic oscillator, that seem out of place in an undergraduate book. Students with a weak command of calculus and no desire to improve it may find Sönke Johnsen’s excellent The Optics of Life (2011) more palatable.

A neural synapse. Painting by David S. Goodsell, as published in From Photon to Neuron: Light, Imaging, Vision by Philip Nelson. Copyright © 2017 by Philip C. Nelson. Reprinted by permission of Princeton U. Press.

A neural synapse. Painting by David S. Goodsell, as published in From Photon to Neuron: Light, Imaging, Vision by Philip Nelson. Copyright © 2017 by Philip C. Nelson. Reprinted by permission of Princeton U. Press.

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The wave and particle properties of light are both crucial to biology. For instance, diffraction limits visual acuity, but a rod cell in the retina responds to a single photon. Nelson adopts a perspective like the one Richard Feynman presented in QED: The Strange Theory of Light and Matter (1985): Photons are governed by a probability amplitude that obeys a stationary-phase principle. That powerful point of view highlights the intimate relationship between quantum mechanics, probability, and vision. Physics students will appreciate it; I am not sure what biology students will make of it. For me, it works. Its disadvantage is that you must add a lot of e terms to explain simple concepts like reflection and refraction.

Readers who are interested in vision but have little concern for light or imaging might prefer Robert Rodieck’s masterpiece The First Steps in Seeing (1998). The books by Rodieck and Nelson share several characteristics: eloquent prose, outstanding artwork, and a quantitative approach that most biology textbooks lack. Nelson’s book, however, is more useful for teaching; it includes homework problems, end-of-chapter summaries, and recommendations for additional reading.

Nelson’s emphasis on computer code—or at least his insistence that the students write their own code—also sets his books apart. Many of his homework exercises require analyzing data that you can download from the author’s website ( To do those exercises, you must know how to program a computer using MATLAB or similar software, and you can download Nelson’s free Student Guide to MATLAB from his website. Computerphobes may hesitate initially, but they will gain the most from numerical modeling. Nelson uses words, pictures, formulas, and code to teach students how to construct models and interpret data. His books provide a master class in how to integrate those four different approaches into a complete learning experience.

Overall, I found From Photon to Neuron to be an outstanding textbook and a worthy successor to Biological Physics and Physical Models of Living Systems. Philip Nelson has done it again.

Brad Roth is a professor of physics at Oakland University and is coauthor with Russell Hobbie of Intermediate Physics for Medicine and Biology (2015)