Voigt’s new group, called Neurophotonics, will begin its work in October 2026 and will occupy a unique position at the interface of physics and medicine. The team will be jointly anchored at MPL, one of the world’s leading institutes for photonics, and the MPZPM, a collaborative research center of MPL, Friedrich-Alexander-Universität Erlangen-Nürnberg, and Universitätsklinikum Erlangen. This dual affiliation is no accident. Voigt’s research sits precisely at the boundary between cutting-edge optical engineering and fundamental neuroscience, and he argues that the Erlangen ecosystem offers an unusually good environment for both halves of his agenda.

“For me, the Max-Planck-Zentrum für Physik und Medizin is the ideal place to pursue my main interest – bringing together the worlds of photonics and neuroscience,” Voigt says. “The funding from the ERC Grant not only supports the establishment of my research group. Our new instruments will be freely accessible to the scientific community as an ‘open hardware’ project and will be applied to a wide range of questions, not only in neuroscience.”

The scientific problem that Voigt has set his sights on is deceptively simple to state. The human brain, weighing on average 1.5 kilograms and containing more than 23 billion nerve cells, remains the most complex object we know of in the biological universe. It governs sensory processing, motor control, and every behavior an organism produces. Yet despite decades of progress in neuroscience, exactly how the brain translates sensory input into a specific behavioral response is still an open question. Part of the difficulty is methodological: observing a brain at work usually means observing it under conditions that are anything but natural.

Optical microscopes can capture the activity of individual neurons in living animals with extraordinary precision, and over the past two decades techniques such as two-photon and light-sheet microscopy have transformed what neuroscientists can see. But there is a catch. In most conventional setups, the animal under observation cannot move freely. Head-fixed preparations, treadmill-like arrangements, and immobilized larvae allow exquisite imaging, but they constrain the very behaviors researchers want to understand. An animal that cannot navigate its environment cannot display the natural patterns of neural activity that navigation entails. Insights into information processing under natural conditions are therefore severely limited.

This is the bottleneck that KALEIDOSCOPE is designed to break. The project aims to develop a new generation of optical microscopes capable of recording brain activity in freely moving animals – a capability that, if realized, would allow neuroscientists to watch neural circuits operate in real time, in three dimensions, and in the natural behavioral context that has been missing from most laboratory imaging. To get there, Voigt’s team will combine three technological pillars: state-of-the-art image processing, advanced microscopy, and optical nanostructures. The centerpiece of the engineering effort involves metasurfaces – engineered surfaces patterned with nanostructures that can manipulate light in ways conventional lenses cannot – to build instruments that can track an animal’s movements in three dimensions with exceptional speed and precision while simultaneously mapping the activity of individual neurons.

The challenge is formidable. To image neurons in a brain that is itself moving through space, a microscope must effectively stabilize its view against the animal’s own motion, keep rapidly moving cells in focus, and collect enough photons to detect the faint fluorescence signals that report neural activity – all in real time. Solving these problems will require not only novel optical designs but also sophisticated computational pipelines capable of deconvolving the animal’s motion from the recorded signals. Voigt’s background, which spans both neuroscience and instrument development, positions him to attack the problem from both ends simultaneously.

But KALEIDOSCOPE is not merely a technology project. The new instruments will be pointed squarely at some of the most intriguing open questions in neurobiology: How do animals perceive three-dimensional space, and how do they navigate within it? Which species are capable of creating cognitive maps – internal representations of the external world that allow flexible navigation? How does spatial cognition emerge, and how does it change over the course of an animal’s development? By imaging whole-brain activity in animals that are free to explore their surroundings, Voigt’s group hopes to watch these cognitive capacities take shape as they happen.

The model organisms at the heart of this effort are as remarkable as the instruments. At MPZPM, Voigt will have access to the “In Vivo Model Systems” core facility, which already houses state-of-the-art fish breeding systems for zebrafish larvae, Danio rerio, long a staple of developmental neuroscience because of their optical transparency and rapidly developing nervous systems. Alongside them will move Danionella cerebrum, one of the smallest known vertebrates. At roughly one centimeter in length, Danionella is small enough to be a serious candidate for whole-brain imaging in a moving animal, while still possessing a brain complex enough to exhibit interesting behaviors. Its diminutive brain, combined with transparency during early life, makes it an ideal subject for the kind of metasurface-based brain observatories the ERC grant will fund.

Voigt will not be starting from scratch on the neuroscience side of the campus. At MPZPM he joins two established research teams already working on the brain. Prof. Kristian Franze, head of the “Neuronal Mechanics” division, investigates how cellular forces, the local mechanical properties of cells and tissues, and cellular mechanosensitivity contribute to the development of the central nervous system. Prof. Tomohisa Toda leads the “Neural Epigenomics” group, which studies how age-related impairments of neurons can lead to neurological and psychiatric disorders, with the aim of unraveling the fundamental mechanisms of brain function during aging. The presence of these complementary groups creates an environment in which mechanical, epigenetic, and now photonic approaches to the nervous system can cross-fertilize.

The wider significance of the project lies in its dual promise. On the one hand, KALEIDOSCOPE addresses a fundamental biological question – the neural basis of spatial perception and navigation – that touches on everything from how a larval fish hunts to how humans form memories of places. On the other, it is an ambitious instrument-building program whose products are intended to outlive the specific experiments that inspired them. By releasing the new microscopes as open hardware, Voigt’s team aims to make freely moving brain imaging a tool available to the entire scientific community, applicable to questions far beyond neuroscience itself.

The ERC Starting Grant, one of Europe’s most competitive funding instruments for early-career researchers, is designed precisely to enable such risk-taking, high-reward programs at the start of an independent scientific career. Combined with the Max Planck Society’s transatlantic support, it gives Voigt the resources to recruit an interdisciplinary team of scientists and engineers – a mix that will be essential, since the project demands expertise in optics, nanofabrication, computer vision, and systems neuroscience all at once. The two main goals of the group reflect this breadth: developing imaging instruments capable of visualizing and studying the brain’s complexity as a whole, and using those instruments to answer deep questions about spatial cognition and its development.

For the researchers and engineers who will join the Neurophotonics group, the coming years promise the rare opportunity to build an entirely new class of scientific instrument while simultaneously using it to explore questions that have fascinated scientists for generations. For the wider community, the bet is that a one-centimeter fish, a metasurface, and an open-hardware ethos can together crack open a window onto the brain as it has never been seen before – not fixed, not restrained, but alive, moving, and thinking in three dimensions.