Over the last decade the existence of "the corona," a natural interface between nanomaterials and living matter in biological milieu, evolved from a vague concept into broadly recognized fact. This robust shell arises (to some extent) on the surface of all nanoparticles (NPs), even the ones designed to avoid its formation upon contact with biological fluids and confers a biological identity to the nanomaterials such that they can engage with cellular machinery. The NP corona consists of those proteins (and other biomolecules such as lipids and sugars) residing on the NP surface for a sufficient timescale to influence the NP's properties and interactions with living systems. This chapter aims to provide simple protocols, as well as notes on potential pitfalls, to help researchers to perform basic experiments in this field as the basis for a more mechanistic approach to study and understand NP-protein corona complexes. This work has been supported by INSPIRE (Integrated NanoScience Platform for Ireland) funded by the Irish Government's Programme for Research in Third Level Institutions, Cycle 4, National Development Plan 2007-2013, and 3MICRON (NMP-2009-LA-245572), NAMDIATREAM (NMP4-LA-2010-246479) and QualityNano (INFRA-2010-262163) funded by the European Commission 7th Framework Programme.