Electrons in monolayer graphene are described by massless Dirac electrons, which exhibit unique quantum phenomena due to the pseudospin and Berry phase of the massless electrons. In this talk, I will discuss our effort in probing massive Dirac electrons in gapped bilayer graphene, which can be described by a quantum valley Hall insulator with non-trivial Chern number for individual valleys. We show that a tunable bandgap up to 200 meV can be induced in bilayer graphene with electrical gating. In addition, we observe a topologically protected 1D conducting channel at the domain boundary of AB-BA bilayers, which can be attributed to the quantum valley Hall edge states in gapped bilayer graphene. I will also discuss one-dimensional plasmon arising from Luttinger liquid of Dirac electrons in metallic carbon nanotubes, which exhibit semi-quantized propagation speed and remarkable sub-wavelength plasmon confinement.