Diffusion-limited aggregation: a kinetic critical phenomenon?

Diffusion-limited aggregation (DLA) is a model which represents noisy growt h limited by diffusion. This process is quite common in nature and the simp le algorithm gives a good representation of the large-scale structure of ma ny natural objects. The clusters grown in the computer and the real objects in question are tenuous and approximately self-similar. A good deal is kno wn about the algorithm, but a complete theory is not yet available. I revie w the current state of knowledge about the model, its applications and theo retical analysis of the results.