Meaning: Fireflies are small, but they have a big impact on the environment and our lives.
Choice of Words: Tiny creatures: very small animals, big impact: a large or important effect.
Alternative Expressions
Small but mighty.
Meaning: This means that something is small but still very powerful.
Choice of Words:Small means not very big. But is used to connect two contrasting ideas. Mighty means very powerful or strong. When you put them together, "Small but mighty" means that something is small in size but has a lot of power or strength.
Don't judge a book by its cover.
Meaning: This means that you shouldn't judge something based on how it looks, because it might be different on the inside.
Choice of Words:Don't means to not do something. Judge means to form an opinion about something. Book is something you read that has a story or information in it. Cover is the outside part of a book that protects the pages. When you put them together, "Don't judge a book by its cover" means that you shouldn't form an opinion about something just by looking at its outside appearance.