This paper presents a method to simulate growth phenomena, and its application to the modeling of complex organic shapes (e.g., plants organs) and folded surfaces. Our main contribution is the interactive and stable resolution of the mechanical problem of growth-induced deformations, based on the minimization of the energy due to the various constraints in the shell. >From this, we propose a new modeling approach based on a set of growing tools: The user can apply 'hot spots', 'hot curves', or paint growing parameters on the surface to grow. Growth can be simulated either simultaneously to the user interaction, or once all parameters have been settled on the surface (which allows the use of textures of parameters and procedural operations). The main parameters are the intensity and anisotropy of growth, as well as their variations over time. Geometric constraints and plasticity can also be considered. As our results show shapes can fold, bend, and curl as in nature, which deforming tools such as displacement map could not achieve. We demonstrate our tool with an interactive session and a gallery of shapes easily produced.