Concrete has been formed in rigid molds since its invention in Ancient Rome. Very recently however, the possibility of a new architectural and structural language has emerged based on the use of flexible fabric formworks that are shaped by an internal response to the weight and pressure of wet concrete. This way of building results in works of great simplicity, economy, and beauty. This lecture will present many examples of this approach to construction and design, and explore the methods of discovery used at the Centre for Architectural Structures and Technology (CAST), in Winnipeg, Canada