This lecture explores the design and construction of tridimensional trusses, showcasing examples from EPFL's structures and beyond. The instructor explains the principles behind truss nodes, compression, and tension forces, illustrating how these structures are used in bridges, geodesic domes, and large-scale roofs. The lecture delves into the challenges of complex nodes and variable bar lengths, while highlighting the efficiency and versatility of tridimensional trusses for creating lightweight, spacious structures in various contexts.