In BAT, lipid droplets and mitochondria form extensive contact sites that coordinate lipid metabolism and thermogenesis. However, the molecular composition, regulation, and functional significance of these contacts remain poorly understood. Using our C-COMPASS organelle proteomics platform, we generated global maps of organelle remodeling during thermogenic activation and identified novel LD-mitochondria contact site proteins. We will combine organelle proteomics, lipidomics, metabolomics, complexome profiling, phosphoproteomics, and genetic models to define the architecture, dynamics, and function of LD-mitochondria contact sites and associated mitochondrial subpopulations. This project will uncover how organelle interactions drive mitochondrial specialization and spatial metabolic compartmentalization in BAT.