Clouds display striking forms of organization on the mesoscale (a scale ranging typically from 2 to 200 km). Far from being a mere curiosity, this organization challenges our understanding of atmospheric physics and climate. What processes control cloud patterns and organizations? How much does the mesoscale organization of convection matter for climate? I will show how new observations from satellites and field campaigns shed light on how and why clouds organize at the mesoscale. Then, based on simulations from a new generation of climate models, I will explore the role that this mesoscale organisation might play in climate and climate change.