The question of relationships between scientific expertise, society and politics fundamentally revolves around communication. Though often presented as unequivocal and indisputable, expert scientific opinions do not put an end to controversy. They are developed in the context of relationships that are always uncertain, involve many different stakeholders with an interest in the object of the controversy and exist in a social situation. The resulting knowledge shapes narratives that can be interpreted and framed in many different ways, each reflecting different reasons for action, conflicting economic and political interests, tensions or disputes. This process takes place in close conjunction with the activities of the media and networks, through which expert conclusions are broadcast and increasingly debated.