Some layered Van der Waals materials, such as transition metal dichalcogenides have intrinsically large r s values which exceed the 2D theoretical Wigner crystal limit r s =31~38. The origin of the large r s is partly due to the suppressed kinetic energy arising from a strong electron phonon interaction which leads to polaronic band narrowing, and partly due to the low carrier density n at low temperatures. The charge density wave (CDW) state in such materials, such as 1T-TaS 2, with a sparsely filled √13x√13 superlattice and r s =70~100 may be considered to be better described in terms of a Wigner crystal than the more traditional charge density wave. This viewpoint is supported both by modelling and systematic scanning tunnelling microscopy measurements. Thus, Wigner crystal superlattices in so-called CDW systems may be considered to be the first direct observation of ordered electron states localised by mutual Coulomb interaction. An important criterion for is the depth of charge modulation, which depends on the material, and only systems where r s exceeds the theoretical limit can be regarded as Wigner crystals.