With their reduced dimensionality, 2D materials exhibit exotic electronic and optical properties due to strong electron confinement and correlation effects. Modern synthesis techniques enable stacking of various 2D materials (semiconductors, semimetals, and insulators) in predefined sequences, leading to a wealth of novel devices & applications. Tailoring the properties of these so-called van der Waals heterostructures postgrowth would greatly benefit from a modification technique with a monolayer precision. To achieve such control, slow highly charged ions (HCI) appear ideal as they carry high amounts of potential energy, which is released rapidly (i.e. within the first few atomic layers) upon ion neutralization. Indeed, when irradiating a free-standing MoS2/graphene heterostructure with HCI we find that nm-sized pores are only produced in the MoS2 monolayer facing the ion beam, while the graphene underneath stays intact*. This contribution will show recent results on HCI-driven perforation of 2D materials and vdW heterostructures and discuss possible damage mechanism.