In this paper, the critical behavior of the percolation models is reviewed, with emphasis on the scaling laws present and its relationship with other simple models like the Ising magnet. A liitle bit of the history and some examples of its application are given to illustrate the range of phenomena that can be described with such models.

Quite an industry has developed around the study of nonlinear phenomena occurring at the threshold of black hole formation first discovered by Choptuik [1]. A number of reviews detail the substantial progress in understanding these phenomena [2,3]. By specifying a form of initial data parameterized by some parameter p, numerical evolutions can determine whether the value of p is sufficient to f...