This chapter provides a comprehensive overview of intellectual capital (IC) and its application at the micro, meso, and macro levels. It traces the historical development of IC theory and practice from its origins in firm-level management to its expansion to industries and nations. The constituent parts, objectives, and insights gained from applying the IC lens at each level are examined. Key models for measuring and managing IC are reviewed, along with critiques of the IC approach. The unique benefits of the IC perspective are highlighted, while also acknowledging its limitations. The chapter concludes by reflecting on future directions for IC research and practice, including opportunities to refine measurement frameworks, address global challenges, and leverage new technologies. Overall, this analysis demonstrates the continued relevance of IC as a framework for understanding and leveraging intangible assets to drive value creation, innovation, and competitiveness across organisational, sectoral, and national contexts.