We propose a model of a self-avoiding growing string with excluded vol
ume effects. In this model, the string develops to form a complex shap
e like a labyrinth. We find simple dynamical scaling relations for sev
eral characteristic quantities, including the radius of gyration and r
adius of curvature. Detailed numerical calculations show that there ar
e two length scales and one time scale characterizing the shape transf
ormations of the growing string.