Eggs are of particular interest in nutrition because they contain all the nutrients necessary for human health, except for dietary fibre and vitamin C. The aim of this chapter is to discuss current trends in the study of nutritional and physiological functions of egg yolk. In particular, we will focus on the bioactive components derived from egg yolk (focusing on proteins/peptides and lipids), issues related to egg cholesterol and recent applications of IgY. Research on other areas such as sialic acids and lutein is covered, although in less detail. To place these trends in context, a brief overview of background knowledge about egg yolks is also provided. This chapter updates and expands on the review provided by Hatta et al. (2008).