* A book. Books are often seen as a symbol of knowledge and understanding. Reading a book can help us to learn new things and gain a deeper understanding of the world around us.

* A light bulb. A light bulb represents a sudden moment of understanding, or an "aha!" moment. When a light bulb goes on, it means that we have suddenly understood something that we didn't understand before.

* A key. A key represents the ability to unlock something, such as a door or a puzzle. In a metaphorical sense, a key can also represent the ability to unlock our understanding of something.

* A puzzle piece. A puzzle piece represents a small part of a larger whole. When we put together all the puzzle pieces, we can eventually see the whole picture and understand it.

* A mirror. A mirror reflects our image back to us. In a metaphorical sense, a mirror can also represent our ability to reflect on ourselves and our own understanding.