Daylight is not only fundamental for architecture and renovations, modernizations and transformations of cities and buildings - it is fundamental for people's well-being. This paper describes the significance of daylight to people. Based on a qualitative research project in Denmark in 2012 about the use of windows among 13 families I will show how daylight is perceived, used, coped with, and negotiated by people in their homes, thus exploring the social character of a natural phenomenon. A metaphor will be used from biomimetics, claiming that - like plants - the Danish participants need daylight. People's day-to-day entanglements with daylight are illustrated, highlighting the social qualities of daylight. The paper concludes that access to daylight is vital for existential reasons (health, social reasons and to feel connected to one's natural environment), showing the window as much more than a technical artefact. Based on this I argue for the window to be acknowledged as vital for creating dwelling and for its inclusion in bio-inspired design and biophilic architecture that so far have focused more on the inclusion of nature and views to greenery, less on daylight.