Previous studies on heart growth and development have elucidated important gene- and cellular-level changes. The development of improved biochemical, mathematical, and computational methods has enabled more accurate elaboration of the structural and functional processes of the heart. Systematic analyses of heart complexity have revealed the differences between normal and pathological growth and development in terms of self-organizational ability, energy balance, clock regulation, and heart rate variability. The present study summarizes what is known about cardiac behaviors and characteristics during heart growth and development. The results indicate that the heart demonstrates systematic complexity, and suggest that new characteristic analyses and treatments of heart diseases can be expected in the future.