Cold temperatures and unexpected frost events cause billions of dollars in agricultural losses each year and limit where crops can be grown. Plants survive freezing conditions by protecting their cellular membranes, which are highly sensitive to temperature and dehydration. This project seeks to understand a natural strategy plants use to survive freezing: the production of unusual membrane lipids in chloroplasts during cold stress. These lipids appear only during freezing and disappear when temperatures recover, suggesting they provide a temporary but critical protective function. By uncovering how these lipids stabilize membranes, this work will advance fundamental knowledge of how living systems adapt to environmental stress. The results have broad societal relevance, including informing the development of cold-tolerant crops that would improve food security, reduce economic losses, and expand agricultural production into new regions. In addition, the findings may inform technologies in medicine, such as improved preservation of cells and tissues, and in materials science, where freezing processes are widely used. The project also supports interdisciplinary training of students and engages the public through educational outreach on plant resilience and climate adaptation. This project will determine how tri- and tetra-galactolipids (TGDG and TeGDG), which accumulate in chloroplast membranes during freezing, contribute to membrane stability at low temperatures. The central hypothesis is that the unique combination of large sugar headgroups and highly unsaturated fatty acid chains in these lipids enables membranes to maintain hydration, fluidity, and resistance to damaging phase transitions. To test this, the research integrates molecular dynamics simulations, biophysical experiments, and plant genetic approaches. First, the project will quantify how TGDG/TeGDG headgroups alter membrane hydration, lipid packing, and fusion propensity using simulations, Langmuir