Universality and scaling are two important concepts in the theory of c
ritical phenomena. It is generally believed that site and bond percola
tions on lattices of the same dimensions have the same set of critical
exponents, but they have different scaling functions. In this paper,
we briefly review our recent Monte Carlo results about universal scali
ng functions for site and bond percolation on planar lattices. We find
that, by choosing an aspect ratio for each lattice and a very small n
umber of non-universal metric factors, all scaled data of the existenc
e probability E(p) and the percolation probability P for site and bond
percolations on square, plane triangular, and honeycomb lattices may
fall on the same universal scaling functions. We also find that free a
nd periodic boundary conditions share the same non-universal metric fa
ctors, When the aspect ratio of each lattice is reduced by the same fa
ctor, the non-universal metric factors remain the same. The implicatio
ns of such results are discussed.