* They are the fundamental units of matter: Just like bricks are the basic units for building a house, atoms are the basic units for building everything in the universe. Everything around us, from the air we breathe to the chair you're sitting on, is made up of atoms.

* They combine to form molecules: Atoms can bond with each other to form molecules, just like bricks can be stacked and joined together to form walls and structures. Water, for instance, is formed from two hydrogen atoms and one oxygen atom.

* They have different properties: Different types of atoms (elements) have different properties, just like different bricks have different sizes, shapes, and strengths. Some atoms are small and light, while others are large and heavy. Some are reactive, while others are stable.

* They can be arranged in different ways: Atoms can be arranged in different ways to create different substances. Think of a house – the same bricks can be arranged in different ways to create different rooms, floors, and styles. Similarly, the arrangement of atoms determines the properties of a substance.

* They are constantly in motion: Like building blocks that can be moved and rearranged, atoms are constantly in motion, vibrating and interacting with each other.

So, just as a complex structure is built from a collection of bricks, the universe, and everything in it, is built from a collection of atoms.