Design for behavioural change is a field of growing importance. Its growth is driven, on the one hand, by the fact that most of the problems we face as humanity are behaviour-based (e.g. threats to sustainability, health and well-being), and on the other by the notion that well-designed interventions can support people in changing their behaviour in the desired direction. This development has led to a growing number of design professionals, institutes and governmental organisations focusing on designing for behaviour change and consequently to a growing need for methodological support. The Behavioural Lenses Approach is one such recent initiative towards a method that allows designers to use theory from the behavioural sciences to inform their work. Together with partners from creative industry and academia, we developed a theoretical framework [(Hermsen, Renes, & Frost, 2014)][1] and a toolkit [(Hermsen, 2015)][2] based on 5 so-called 'lenses', which relate to five general aspects of behaviour (change): Habits and Impulses; Knowing and Believing; Seeing and Realising; Wanting and Being Able To; Doing and Persisting. The toolkit has been used in a broad range of projects in practice and academic research (e.g. [Hermsen, Renes & Frost, 2014][3]; Hermsen et al., [2015][4], [2016][5]; [Van Essen, Hermsen, & Renes, 2016][6]; [Ploos van Amstel et al., 2017][7]). This repository offers an overview of all publicly available tools, cases, papers, and other materials.   **How do you use the Behavioural Lenses?** The Behavioural Lenses can play a role in every phase of the design process. In this text, we use the [Double Diamond process model][8] to describe the use of the Lenses in each phase.   *Discover (explore) phase* There are different ways in which the Behavioural Lenses can help you with the target group research prior to the design phase. - You can use the lenses to define the target behaviour (see sheet [Target Behaviour Canvas][10]), - You can use the lenses to get an idea of what you already know about the target group and behaviour, what assumptions you have about this and what questions you still need to ask the target group ([Behavioural Lenses Poster Tool][11]). - You can use the lenses to analyse insights from literature and target group research (Research Wall, to be added) How do you determine the target behaviour based on the Behavioural Lenses? Case: to be determined How do you determine which stakeholders play a role in behavioural change? Case: [NAM – safety at work][12] How do you use the Behavioural Lenses when setting up your target group research? What do you already know about the target group and behaviour, what assumptions do you make and what do you need to figure out? Case: to be determined How do you use Behavioural Lenses in the analysis of insights from target group research? Case: [Cycling with Focus][13] When do you not use the Behavioural Lenses? Text: When not to use the Behavioural Lenses Tools: [Target Behaviour Canvas][14] [Behavioural Lenses Poster Tool][15]  Research Wall exercise (to be added)   *Define phase* How do you use the Behavioural Lenses when choosing an appropriate strategy for behavioural change? We investigated this in the SIA/RAAK-kiem-funded project Design with Fundament. In this project we designed some prototypes with which you can make an evidence-based choice for a behavioural change strategy, based on insights obtained from the use of the lenses in the Discover phase. The most recent prototype, the Pathfinder, is available from our website. Tool: Pathfinder: [https://www.sander-hermsen.nl/playground/pathfinder/][16] To host your own version of the Pathfinder tool ([GNU Public Licence 3.0][17]), or to develop this tool further, please find the source code here: [https://osf.io/xg3vh/][18]   *Develop phase* How do you use the lenses when evaluating your concept ideas? Do your concept ideas match the insights you gained in earlier phases? Case: to be determined Tool: Behavioural Lenses Concept Evaluation poster tool – Available in Dutch; English soon(ish) Behavioural Lenses Sticker Tool [Available in Dutch][19]; English soon(ish)   *Deliver and Evaluation Phases* How do you use the lenses to evaluate the acceptance and effect of your design? Case: to be determined   **Do you want to contribute to the Behavioural Lenses Approach?** Have you used the tools and do you have feedback, or do you want to share your experiences? Have you developed your own tool(s) and do you want to make them publicly available? Have you published work with the Behavioural Lenses in scientific or professional publications? Please let us know! You can use the comments section to reach us, or drop us a line at sander.hermsen@hu.nl [1]: https://osf.io/adrhs/ [2]: https://medium.com/@sanderhermsen/how-can-we-support-designers-to-create-theory-driven-designs-for-behaviour-change-the-persuasive-a8e3f5a5f6de [3]: https://osf.io/adrhs/ [4]: https://osf.io/dmfj3/ [5]: https://osf.io/fg2sy/ [6]: https://osf.io/zagcx/ [7]: https://osf.io/a3ch9/ [8]: https://en.wikipedia.org/wiki/Double_Diamond_%28design_process_model%29 [9]: https://mfr.de-1.osf.io/render?url=https://osf.io/3bqpj/?action=download&mode=render [10]: https://osf.io/7xkvu/ [11]: https://osf.io/t4mkd/ [12]: https://osf.io/fkxq2/ [13]: https://osf.io/tduq2/ [14]: https://osf.io/7xkvu/ [15]: https://osf.io/t4mkd/ [16]: http://ttps://www.sander-hermsen.nl/playground/pathfinder/ [17]: http://www.gnu.org/licenses/gpl-3.0.html [18]: https://osf.io/xg3vh/ [19]: https://osf.io/83xsa/