Q: Given a scientific passage and an answer, generate a question for the given answer.
Passage: Living things are made of matter. In fact, matter is the "stuff" of which all things are made. Anything that occupies space and has mass is known as matter. Matter, in turn, consists of chemical substances. A chemical substance is a material that has a definite chemical composition. It is also homogeneous, so the same chemical composition is found uniformly throughout the substance. A chemical substance may be an element or a chemical compound. Answer: matter
A:
What is the 'stuff' that all things are made of?