Abstract: It has long been known that holomorphic field theories on twistor space lead to “physical” field theories on Minkowski space. In this talk I will discuss a type I (unoriented) version of the topological B model on twistor space. The corresponding theory on Minkowski space is a sigma-model with target the group SO(8). This is a variant of the Skyrme model that appears as the low-energy effective theory of mesons in QCD. (The group SO(8) appears because of the Green-Schwarz mechanism in the topological string). The origin of this model in the topological string implies many remarkable properties. For one thing, the model is, in a certain sense, integrable. Further, although the Lagrangian is power-counting non-renormalizable, counter-terms at all loops can be uniquely fixed.