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

Plasma matter makes up most of the universe.
What type of matter makes up most of the universe?

Protists are thought to be the oldest eukaryotes.
What is thought to be the oldest eukaryotes?

It solidifies happens to a substance in a liquid state when the temperate is lowed.
What happens to a substance in a liquid state when the temperate is lowed?