How to explore inaccessible places by swarms of sensors

Since the dawn of humankind, exploration of certain places, ranging from the depths of the oceans to the edges of the universe, has led to numerous discoveries. However, there are also several environments that need to be examined but can't be directly observed, like chemical or nuclear reactors, underground water or oil distribution pipes, space and inside of the body. The EU-funded Phoenix project has been addressing this challenge by developing a new line of technology that will offer the opportunity to get to unreachable places.