Social Innovation and Entrepreneurship in the Fourth Sector -- Part I: Consolidation of the Fourth Sector Within the Solidarity Economy -- Humanitarian Social Logistic and the Fourth Sector: Policy Design for Communities Affected by the Disaster -- Nonprofit Organizations of the Fourth Sector That Promote Education Social Solidarity Economy in the Fourth Industrial Revolution of Medellin, Colombia -- Social Innovation, Fourth Sector and the Commodification of the Welfare State: The Portuguese Experience -- Part II: Best-Practices Case Studies Across the World -- A Case Study of a Socially Responsible Entrepreneurship: The Local Action Group POEDA -- Case Study: How Medellin Is Creating a Hub for Impact Start-ups -- The Behobia/San Sebastián Race: Running Past the Boundaries of Sport -- The Project Partnership for Local Development: The Fourth Sector and Hybrid Initiatives -- Social Innovative Approaches on Health Care: Evidence from Home Hospitalization in Portugal-the Elvas Study -- Havířov: "The City of Green" and Its Fourth Sector Sustainability Activities. One Case Study from the Czech Republic -- Commitment to Social Responsibility in a Third Sector Organization: The Case of Alfazema Flower -- Part III: Discussion About Social Innovation and Business -- Sustainability Perspective Through Social Responsibility in Microenterprises of Tulancingo, Hidalgo, Mexico -- Social Innovation: Insights in the Fourth Sector in Portugal -- The Fourth Sector and the 2030 Strategy on Green and Circular Economy in the Region of Extremadura -- Marketing for Business Opportunities Management on Foreign Investment and Productive Enchainments.