English: When graphene is epitaxially grown on the (111) surface of iridium it shows long-wavelength height modulation that can be thought of as a moiré pattern arising from the superposition of the two mismatched hexagonal lattices. Flat graphene has lattice constant of 0.246 nm, and Ir(111) 0.272 nm. Moiré periodicity is 2.5 nm.