This paper discusses the electronic structure of a bilayer graphene with a small-angle twist between the two layers. The authors derive the conditions for the formation of periodic Moiré superlattices and formulate a continuum description using massless Dirac fermions coupled by slowly varying inter-layer hopping. They find that the low-energy electronic structure differs significantly from that of an $AB$-stacked bilayer, with a reduced Fermi velocity ($v_F$) compared to single-layer graphene. Additionally, they show that an external electric field does not open a gap in the electronic spectrum, which is consistent with observations in epitaxially grown graphene. The study highlights the profound impact of small stacking defects, such as rotations, on the low-energy properties of bilayer graphene.This paper discusses the electronic structure of a bilayer graphene with a small-angle twist between the two layers. The authors derive the conditions for the formation of periodic Moiré superlattices and formulate a continuum description using massless Dirac fermions coupled by slowly varying inter-layer hopping. They find that the low-energy electronic structure differs significantly from that of an $AB$-stacked bilayer, with a reduced Fermi velocity ($v_F$) compared to single-layer graphene. Additionally, they show that an external electric field does not open a gap in the electronic spectrum, which is consistent with observations in epitaxially grown graphene. The study highlights the profound impact of small stacking defects, such as rotations, on the low-energy properties of bilayer graphene.