Galaxies are an exotic mix of stars, gas, and an unseen dark component called dark matter. Our own Milky Way galaxy is no different; an invisible dark matter halo extends out to thousands of light years, confining 100 billion stars in its centre. However, despite this halo being largely invisible, records of the Milky Way's past are scattered around the halo in the form of satellite galaxies and halo stars. The Milky Way is a cannibal; throughout its lifetime it captures and destroys smaller dwarf galaxies. The remains of destroyed dwarfs are splayed out in a diffuse stellar halo, while the few lucky ones evading destruction comprise the satellite galaxy population that orbits the Galaxy. These halo populations provide a unique opportunity to decipher the accretion history of the Milky Way with a level of detail that cannot be achieved in any other galaxy. Furthermore, the proximity of the dwarf satellite galaxy population provides the only direct probe of structure formation at the low-mass end. These faint galaxies currently present the biggest challenge for our current theories of structure formation, and it is in our own backyard where we must confront this prevailing theory with observations. One of my main research goals is to use both halo stars and dwarf galaxies to unravel the past "eating habits" of the Galaxy. At present, we lack a convincing answer to this fundamental question: How was the Milky Way assembled? My research uses a combination of ground and space-based observational facilities coupled with state-of-the-art cosmological simulations in order to pin down the nature of the Milky Way halo's building blocks.