This white paper is the product of the CAISE Formal-Informal Partnerships Inquiry Group, which began work during a July 2008 ISE Summit organized by CAISE. Their examination of what the authors call "the hybrid nature of formal-informal collaborations" draws on relevant theoretical perspectives and a series of case studies to highlight ways in which the affordances of formal and informal settings can be combined and leveraged to create rich, compelling, authentic, and engaging science that can be systematically developed over time and settings.