"Despite our great expressive skills, we humans lack an easy way of communicating the 3D shapes we imagine, and even more so when it comes to dynamic shapes. Over centuries humans used drawing and sculpture to convey shapes. These tools require significant expertise and time investment, especially if one aims to describe complex or dynamic shapes. With the advent of virtual environments one would expect digital modeling to replace these traditional tools. Unfortunately, conventional techniques in the area have failed, since even trained computer artists still create with traditional media and only use the computer to reproduce already designed content.Could digital media be turned into a tool, even more expressive and simpler to use than a pen, to convey and refine both static and dynamic 3D shapes? This is the goal of this project. Achieving it will make shape design directly possible in virtual form, from early drafting to progressive refinement and finalization of an idea. To this end, models for shape and motion need to be totally rethought from a user-centered perspective . Specifically, we propose the new paradigm of responsive 3D shapes – a novel representation separating morphology from isometric embedding – to define high-level, dynamic 3D content that takes form, is refined, moves and deforms based on user intent, expressed through intuitive interaction gestures.Scientifically, while the problem we address belongs to Computer Graphics, it calls for a new convergence with Geometry, Simulation and Human Computer Interaction. In terms of impact, the resulting “expressive virtual pen” for 3D content will not only serve the needs of artists, but also of scientists and engineers willing to refine their thoughts by interacting with prototypes of their objects of study, educators and media aiming at quickly conveying their ideas, as well as anyone willing to communicate a 3D shape This project thus opens up new horizons for science, technology and society."