Develop criteria to define each type of cell (e.g. what makes a cardiac cell distinct from non-cardiac cells?), and then identify the different cell types in the heart at a more granular level than just cardiomyocyte, endothelial cell, fibroblast.
Determine the function and role of each cell type, including non-resident cardiac cells such as macrophages.
Understand the developmental processes of each cell subtype, including specification of cardiomyocyte subtypes (eg. what are the transcriptional regulators that lead to the formation of different cardiomyocyte subtypes in the atrial, ventricles, conduction network.)
Understand the migration of the various cell types of the heart (endothelial cells, cardiomyocytes, fibroblasts, smooth muscle cells) during the multi-phasic steps of cardiac development (looping, chamber formation).