  Diffusion Limited Aggregation (DLA) has served for forty years as a
paradigmatic example for the creation of fractal growth patterns. In spite of
thousands of references no exact result for the fractal dimension $D$ of DLA is
known. In this Letter we announce an exact result for off-lattice DLA grown on
a line, $D=3/2$. The result relies on representing DLA with iterated conformal
maps, allowing one to prove self-affinity, a proper scaling limit and a well
defined fractal dimension. Mathematical proofs of the main results are
available in arXiv:2008.05792.
