  The tight-binding model of electrons in graphene is reviewed. We derive
low-energy Hamiltonians supporting massless Dirac-like chiral fermions and
massive chiral fermions in monolayer and bilayer graphene, respectively, and we
describe how their chirality is manifest in the sequencing of plateaus observed
in the integer quantum Hall effect. The opening of a tuneable band gap in
bilayer graphene in response to a transverse electric field is described, and
we explain how Hartree theory may be used to develop a simple analytical model
of screening.
