After the history and exploration of these fantastic horizons, we must fathom the unknown territory into which these discoveries, applications and their resulting risks lead us. This is the fourth episode. Rightly and wrongly, working on the scale of the invisible crystallizes many fears. What are the real risks to individuals and the environment? How can we evaluate them? How can they be measured? Are researchers really aware of the dangers they're exposing us to? What is their thinking, ethically? This nano revolution will jeopardize society as we know it, changing the global economic equilibrium and making Big Brother loom on the horizon . . . What place will citizens then occupy? Will they still have a say?