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

Q: Mechanical waves term describes waves that travel through matter.

A: What term describes waves that travel through matter?
****
Q: When light passes from one medium to another, it changes speed.

A: When light passes from one medium to another, it changes what?
****
Q: Vesicles are used during endocytosis to allow molecules to enter the cell.

A:
What cellular structure is used during endocytosis to allow molecules to enter the cell?
****