This project aims to plant a seed in the minds of children to develop sustainable behaviour now and inspire an attitude of environmental stewardship for the future. Children grow up in a take-make-dispose world driven by consumerism. This world is characterised by the continuous production of new consumer products. This has a significant negative effect on the environment. For a sustainable future, people’s behaviour needs to change. Changing children’s attitude towards toy ownership has been identified as an opportunity to create this behaviour change. This lead to the following design challenge: How can I create an experience that engages children to change their behaviour towards toy ownership to inspire environmental stewardship? One of the most efficient ways to make products more sustainable is by extending product life. Extending product life is put into practice by having children pass on toys they have outgrown. By studying children using the context mapping method it was found that they find it difficult to let go of their unused toys. Extending product life and difficulty to let go are conflicting statements. For children below the age of five this is unavoidable, therefore the target group is children aged 5 - 6 as this is the youngest group possible to set in motion the desired behaviour change. Solution directions for the desired behaviour change were generated. The Toy on adventure concept was selected to further develop as this concept uses a narrative which allows for a perspective shift to occur with the child. A shift from a negative association (losing your toy), to a positive one (allowing your toy to go on adventure). In order to convince the child to participate in the concept, action tendency needs to be recognised. Multiple in-context interventions with the users were performed to find effective action tendencies that facilitate behaviour change. The following design elements were established: the power of growth, storytelling, negative emotions & pride. Using and integrating these design elements, the final design was created: Olli Play. Olli Play is an episodic storybook including action items and supporting props (play mat/bag & headdress) to make it easier for children to pass on toys they have outgrown. The design elements are embedded as follows: Episodic storytelling engages children with the experience of Olli Play. The concept of the power of growth is used in the narrative to make the letting go of toys part of growing up. Negative emotions are used to create a rich experience according to the theory of design for emotion. The use of pride provides the after the fact gratification necessary for the experience to have a lasting effect in order to inspire environmental stewardship. The interaction with the final design was tested in a three day testing session. The results showed that the intended effects were accomplished. As expected, the child experienced great difficulties with the thought of letting go toys at first. But as the interaction progressed throughout the days, the attitude of the child was transformed and the overall experience was perceived to be very enjoyable and the toys were gladly given away. The interaction also sparked interest in environmental stewardship. This way, Olli Play creates immediate sustainable behaviour and inspires the intended attitude of environmental stewardship.