The topic of this thesis is to understand and support creativity in design. While the interdisciplinary field of Human-Computer Interaction has been described as a ‘design-oriented field of research’, it has been argued that our understanding of design is relatively poor. The process of design has been described as involving a certain ‘mystical element’. The ‘mystical element’ of the process of design has been described using terms such as ‘creativity’. With a poor understanding, it is hard to know how best to support creativity. This could impact the processes and outcomes of design. This thesis attempts to increase our understanding of creativity in design, thereby increasing our knowledge of how best to support the creative design process. The thesis develops an understanding of creativity in the forms of a definition of creativity, metrics and measures of creativity and an understanding of the creative process as it is expressed in the activity of design. These contributions are developed throughout the thesis building upon theoretical work and are refined reflecting upon our practical studies. Furthermore, we develop an understanding of how to support creativity in design by eliciting requirements for creativity support tools, based upon our theoretical work and practical studies. The application of these requirements are reflected upon and illustrated through the evaluation of an existing support tool and the design, development and evaluation of our own creativity support tool: Public Social Private Design (PSPD).