In 1987, Pasquier constructed the critical A-D-E lattice models whose 
partition functions are found to be identical to the modular invariant 
partition functions of unitary minimal models in conformal field theory. 
In this talk, I will introduce the A-D-E models and show how to construct 
new models from the existing ones by a process called fusion. The fusion 
procedure is used to construct integrable boundary conditions and to 
derive the functional equations which can be solved to give the spectra of the 
transfer matrices.