We present a data-driven method for interactive simulation and visualization of fibrin fibers, a major component of blood clotting. A fibrin fiber is a complex system consisting of a hierarchy with at least three separate levels of detail. Using measurements acquired with an atomic force microscope (AFM) at the smallest scale in this hierarchy, a physically-based model for the larger scales can be constructed and then simulated. Unlike most traditional work dealing with Monte Carlo (MC) or Molecular Dynamics (MD) simulations, our method makes simplifying assumptions about the simulation and enables interactive visualization of simulated fibers in a virtual environment.