This chapter examines the current knowledge obtained by the application of in vitro digestion protocols (IVDs) to measure the micellarisation of carotenoid-rich food sources. The discussion starts with the definition of the term ‘bioavailability’, which generates scientific and technological information necessary to support the health-through-food idea. An overview of the use of the bioaccessibility function in food and nutrition science and the creativity directed to the development of IVDs is given from a practical point of view, rationalising the inputs from the in vivo physiology of human digestion and the key developments implemented, which are crucial for the successful use of IVDs. Later, the events correlated with the digestion of food lipids are outlined, keeping the in vivo applicability of in vitro data as the thematic thread of the story. The effectors in the micellarisation of carotenoids are subsequently presented, accounting for the significance of food structure, food matrix and processing features, physiological issues and other host-related aspects. The correspondence between the earlier results obtained from in vivo studies with recent outcomes from IVDs is emphasised. The IVDs developed for carotenoids are discussed, introducing elements and references for comparison between them and with the recently launched harmonised IVD.