All things are made up of ??????

Back again blogging my child's questions. Sometimes kids remind us the world is so small that we forget to notice the simplest and smallest things on earth.This time he was more curious on how things are made up of?

DS: What is water made up of? What is inside the water?( looking at the glass of water)
MOM: Hydrogen.oxygen atoms. Atoms are the smallest part on this universe.
Dad: molecules and atoms blah blah.......
DS: Started looking even more deeper into the glass with confused state of mind.

After some time
DS: What is this plastic made of?
Dad: Plastic is made from materials that are got from petroleum oil.
DS: Is it from our car petrol?
Dad and mom: Not really.(we were trying to find an answer to support)
DS: But oil ????( he was in disbelief in looking at the plastic leaf and oil)

Later that night....
DS: what is paper made of?
Dad and mom: cellulose from trees and grasses.And its making.
DS: Yes in olden days they wrote in palm leaves
(was happy we could convince him)
DS: What is inside metal?
Mom: Its time for dinner lets talk in detail tomorrow. Escapeeeeeee

Need time for me to do my homework.Earlier it was physics so could answer him better, now chemistry , an area I need to work hard.