Here's a breakdown:

* Atoms: These are the fundamental building blocks of all matter, including solids, liquids, and gases. They consist of a nucleus (containing protons and neutrons) surrounded by a cloud of electrons.

* Elements: Different types of atoms are called elements. There are over 100 known elements, each with its own unique properties. Examples include carbon, oxygen, iron, and gold.

* Molecules: Atoms can bond together to form molecules. A molecule is a group of two or more atoms held together by chemical bonds.

* Compounds: When two or more different elements combine, they form a compound. Examples include water (H₂O) and carbon dioxide (CO₂).

Solids are formed when atoms are tightly packed together in a fixed arrangement. The strength of the bonds between atoms determines the hardness and other properties of the solid.

So, whether it's a rock, a piece of metal, a tree, or a plastic bottle, it all comes down to atoms arranged in different ways to create different structures and properties.