Mobile impurities immersed in a quantum reservoir with bosonic degrees of freedom play a central role in our understanding of nature, and they are moreover fundamental for several important technologies. For instance, electrons in solids interact with the bosonic lattice vibrations (phonons) forming so-called polarons. In light of this, it is highly desirable to have a flexible tabletop experiment where one can study impurity physics systematically and from a broad perspective. Atomic gases constitute precisely such a system. Specifically, a few atoms immersed in an atomic Bose-Einstein condensate (BEC) realise mobile impurities in a bosonic reservoir. We will explore how such a system can unravel the impurity problem in new regimes and with a level of detail never realised before. This includes investigating the effects of temperature, induced interactions leading to multipolaron states, and showing how the quantum mechanical wave function of the impurity as well as its dynamics can be explored. We shall collaborate closely with the experimental group of Jan Arlt at Aarhus University, which has just observed long-lived impurity atoms in a BEC for the first time worldwide.