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

Example Input: Control rods play an important role in the modulation of the nuclear chain reaction.
Example Output: What play an important role in the modulation of the nuclear chain reaction?

Example Input: The properties of the alkali metals are similar to each other as expected for elements in the same family.
Example Output: The properties of the alkali metals are similar to each other as expected for elements in the same what?

Example Input: A colloid is a homogeneous mixture with medium-sized particles.
Example Output:
A colloid is a homogeneous mixture with medium-sized what?