Building stars on Earth: the potential of nuclear fusion

Is there such a thing as "perfect" energy? With nuclear fusion, the answer is maybe.Fusion energy would be safe to human health, environmentally clean, and essentially limitless. But, developing a sustainable fusion reaction still faces significant engineering hurdles and is likely decades away from becoming a reality.So, where are we in the development of fusion technology? What technical challenges remain? And what practical challenges must be overcome to make fusion a competitive ener...