Geoff Mulgan is director of the Young Foundation in London. He has worked in the UK government and previously founded the thinktank Demos. He is a visiting professor at the London School of Economics, University College London, and Melbourne University. This paper is based on a report titled "Social Silicon Valleys: A Manifesto for Social Innovation," available at <http://www.youngfoundation.org>. Social innovation refers to innovative activities and services aimed at meeting social needs, primarily delivered by organizations with social purposes. Unlike business innovation, which is driven by profit, social innovation is motivated by social goals. Examples include the spread of cognitive behavioral therapy and the Big Issue, which sells magazines to homeless people. The process of social innovation involves three stages: ridicule, opposition, and acceptance. Many social innovations began as radical ideas and have since become mainstream. In the 19th and early 20th centuries, civil society led many social innovations, such as mutual aid, microcredit, and trade unions. Later, governments played a key role in social innovation, such as building welfare states and schooling systems. The pace of social innovation is likely to accelerate in the coming century. More money is flowing into NGOs and civil society, and many social sectors, such as health and education, are growing. These sectors involve commercial, voluntary, and public organizations, with public policy playing a key role. Traditional business models are not suitable for these sectors, and social innovation is likely to be more important than innovation in technology or insurance. Many successful social innovations have moved from the margins to the mainstream, including neighborhood nurseries, Wikipedia, holistic healthcare, microcredit, and community wind farms. However, social innovation remains understudied. While commercial innovation is well-researched, social innovation is rarely studied and often relies on anecdotes. Social innovation is driven by both individuals and broader movements. Individuals like Robert Owen, Octavia Hill, and Michael Young have made significant contributions. Movements like feminism and environmentalism have involved millions of people and many leaders. Both individual and collective efforts are important for social innovation. Social innovation requires understanding needs and identifying potential solutions. Needs can be obvious or less obvious, and they often come from campaigns, observations, or informal movements. Empathy and ethnography are important in understanding needs. Ideas are often tested and refined through trial and error. Social innovation involves prototyping, piloting, and scaling up ideas. Successful ideas are those that can be replicated, adapted, or franchised. Scaling up requires strategy, resources, and support. Governments, businesses, and NGOs all play a role in scaling up social innovations. Assessing and diffusing good ideas is crucial for social innovation. Communication is essential to build support and spread ideas. Good names, brands, and stories help in this process. Social innovations can spread through organic growth, federations, or government support. Learning and evolving are important stages in social innovation. Ideas may change as theyGeoff Mulgan is director of the Young Foundation in London. He has worked in the UK government and previously founded the thinktank Demos. He is a visiting professor at the London School of Economics, University College London, and Melbourne University. This paper is based on a report titled "Social Silicon Valleys: A Manifesto for Social Innovation," available at <http://www.youngfoundation.org>. Social innovation refers to innovative activities and services aimed at meeting social needs, primarily delivered by organizations with social purposes. Unlike business innovation, which is driven by profit, social innovation is motivated by social goals. Examples include the spread of cognitive behavioral therapy and the Big Issue, which sells magazines to homeless people. The process of social innovation involves three stages: ridicule, opposition, and acceptance. Many social innovations began as radical ideas and have since become mainstream. In the 19th and early 20th centuries, civil society led many social innovations, such as mutual aid, microcredit, and trade unions. Later, governments played a key role in social innovation, such as building welfare states and schooling systems. The pace of social innovation is likely to accelerate in the coming century. More money is flowing into NGOs and civil society, and many social sectors, such as health and education, are growing. These sectors involve commercial, voluntary, and public organizations, with public policy playing a key role. Traditional business models are not suitable for these sectors, and social innovation is likely to be more important than innovation in technology or insurance. Many successful social innovations have moved from the margins to the mainstream, including neighborhood nurseries, Wikipedia, holistic healthcare, microcredit, and community wind farms. However, social innovation remains understudied. While commercial innovation is well-researched, social innovation is rarely studied and often relies on anecdotes. Social innovation is driven by both individuals and broader movements. Individuals like Robert Owen, Octavia Hill, and Michael Young have made significant contributions. Movements like feminism and environmentalism have involved millions of people and many leaders. Both individual and collective efforts are important for social innovation. Social innovation requires understanding needs and identifying potential solutions. Needs can be obvious or less obvious, and they often come from campaigns, observations, or informal movements. Empathy and ethnography are important in understanding needs. Ideas are often tested and refined through trial and error. Social innovation involves prototyping, piloting, and scaling up ideas. Successful ideas are those that can be replicated, adapted, or franchised. Scaling up requires strategy, resources, and support. Governments, businesses, and NGOs all play a role in scaling up social innovations. Assessing and diffusing good ideas is crucial for social innovation. Communication is essential to build support and spread ideas. Good names, brands, and stories help in this process. Social innovations can spread through organic growth, federations, or government support. Learning and evolving are important stages in social innovation. Ideas may change as they