What is this is what dreams are made of?

"This is what dreams are made of" is an idiom, not a specific thing like a book or movie. It means something is incredibly wonderful, perfect, or exactly what someone has always wanted. It suggests a feeling of elation and fulfillment, often associated with something seemingly impossible becoming reality.

Its origin is often (but not definitively) linked to the 1939 film The Wizard of Oz. While the exact phrase isn't spoken in the film, the line "Somewhere over the rainbow, skies are blue, and the dreams that you dare to dream really do come true" is very close in meaning and sentiment, and the film's overall tone evokes the feeling captured by the idiom.

Therefore, the phrase is:

• Figurative: It's not literal; you can't physically make dreams out of something.
• Highly positive: It implies extreme happiness and satisfaction.
• Widely used: It's a common expression in everyday speech and writing.
• Historically linked (possibly): Its popularity and meaning are often associated with the aspirational themes of The Wizard of Oz.

When you encounter the phrase, it's a signal that the speaker or writer is describing something exceptionally positive and desirable.