Anisotropic bootstrap percolation

Bootstrap percolation models are Cellular Automata with probabilistic initial conditions. We discuss some results and open problems on  the influence of anisotropy on properties of bootstrap percolation models in two and three dimensions. In particular we discuss  finite-size scaling behaviour and  sharp thresholds. (Joint work with Tim Hulshof, Anne Fey, Hugo Duminil-Copin).