||After the successful isolation of graphene, research on two dimensional (2D) layered crystals has grown considerably because of their unusual physical properties. Such unusual properties have triggered excitement and anticipation to produce emerging optical and electronic devices made of 2D crystals. Beyond 2D layered crystals themselves, one can envision new properties and phenomena arising from the stacking of 2D crystals, heterostructures made layer by layer. Vertical stacks of 2D crystals, also called van der Waals heterostructures, have been made in a precisely chosen sequence. However, studies of the impact of the interaction of between 2D crystals on their physical properties are still needed, and are of paramount importance for the design of any potential applications. In this talk, I will present recent results for superlattice phonons of various 2D heterostructures studied by Raman spectroscopy.