Every kind of matter is made of tiny pieces far too small to see.

Toast is matter, so toast is made of tiny pieces too.

Tiny pieces leave the hot toast and go into the air.

Just after the toast starts: the toast's tiny pieces are in the air right above the toaster. Only the toast's pieces are drawn. The air is made of tiny pieces too.

The pieces spread out through the air. Many pieces are in the kitchen.

Fewer pieces reach the hall and the stairs.

A few pieces reach Marco's bedroom. When some of the pieces reach the inside of his nose, he smells toast.

A minute later: the toast's pieces have spread out through the house. Many are in the kitchen, fewer in the hall, and a few have reached Marco.

Each piece is far too small to see. So Marco sees nothing at all, and the smell seems to come from nowhere.

Scientists call these tiny pieces particles.