Contents: 1. Introduction. 2. Indian Federalism. 3. Evolution, Philosophy and Re-statement of Concepts. 4. Articles 1-4: The Genesis of Federal Polity. 5. Relations between the Union and the States— Constitutional Principles of Structuring as well as Strengthening Federal Scheme. 6. Trade, Commerce and Intercourse—Articles 301-307. 7. Economic Unity and Fiscal Integration. 8. Tax: Who can levy Tax?—Article 265. 9. Federalism vis-a-vis Temporary, Transitional and Special Provisions: Articles 369-371-J. 10. Federalism and Amendment of the Constitution: Article 368. The landmark and path breaking Cases upto 2018 have been presented and analysed from their original sources to familiarize students and research scholars about the modes of citation, factual situations, presentation of memorials and counter-memorials, arguments, judicial opinions both majority and dissenting, precedents and the ratio of the case. The book presents in depth the mosaic of Indian federal structure. The mosaic of Indian federal structure is embedded in achieving the ends of fraternity by promoting the means of dignity of the individual and unity and integrity of the Indian Nation. The mosaic of Indian federal structure is rooted in the expression 'Union of States'. The author opines that all federal Units (States) of federal India, without exception, are mutually friendly reciprocal to each other and not distant from each other. Union and its federal Units (States) are mutually reciprocal friendly and interdependence, not antagonizing, to/on each other and not independent from each other. The federal structure enjoined in the textual Constitution of India by its Founder Authors is magnum opus on the lines of constitutional patriotism. The author submits, "Thus, federalism is a form of government with the potential to cope especially well with the challenges to make Rule of Law a Rule of Life".