In the 101 neighbourhoods of Leiden, Zoeterwoude, Voorschoten, Oegstgeest and Leiderdorp, approachable, bottom-up activities are organized every day around a subject that sparks curiosity. The activities are organised by neighbourhood associations, residents, the education sector or representatives of social organisations. For scientists who want to participate, there are two rules: step out of our institute and do not give a lecture! That way, everyone is challenged to share their knowledge in a playful way.