Short peptides—tiny chains of amino acids, which are the building blocks of proteins—have been found to self-assemble into honeycomb-like fibers with narrow, water-filled channels. These structures, which resemble the hexagonal patterns of beehives, are made from only nine amino acids per peptide. When multiple copies of these short peptides come together, they form fibers with a honeycomb-like interior, where the channels are filled with water. This research was led by scientists from the Max Planck Institute for Polymer Research, the University of Ulm, and Ulm University Hospital, with key contributions from Tanja Weil and Katharina Landfester. The study, published in the journal Nature, was co-authored by Jasmina Gačanin and Francesca Mazzotta. The researchers tested different versions of a nine-amino-acid peptide sequence and discovered that the specific order of amino acids determines how the peptides arrange themselves. This arrangement leads to the formation of hexagonal rings that align side by side, creating a honeycomb-like structure. The fibers formed in this way have many parallel channels, each about five nanometers in diameter. Using cryo-electron microscopy, the team was able to observe how the peptides interlock, revealing the molecular interactions that stabilize the honeycomb pattern. The water inside the channels is not the same as ordinary water. Computer simulations suggest that the water within the channels is more tightly packed and less mobile, with hydrogen bonds lasting longer. This was confirmed through experiments using infrared spectroscopy, which showed that when the fibers are dried, loosely bound water evaporates first, while the more strongly bound water in the channels remains for longer. In contrast, when using a control peptide that forms fibers without channels, water is lost uniformly. By changing the amino acid that lines the channel walls, the researchers were able to adjust how tightly the water inside is bound. Depending on the specific amino acid used, the water inside the channels could be more strongly bound or bound to a similar degree as regular water. Importantly, these modifications did not disrupt the honeycomb structure, allowing the internal environment of the channels to be customized while maintaining the overall geometry of the material. This research provides a foundation for studying how water behaves in extremely confined spaces and opens up possibilities for applications in substance separation or chemical reactions. However, practical applications have not yet been demonstrated. For now, the key achievement is the development of a set of rules for creating complex materials from very short molecular chains.