Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

[EX Q]: The mitochondria organelles are known as the "power plants" of the cell.
[EX A]: What organelles are known as the "power plants" of the cell?

[EX Q]: Cells are the  basic building blocks of the human body.
[EX A]: What are the  basic building blocks of the human body?

[EX Q]: Solar energy travels in photons.
[EX A]:
Solar energy travels in what?