How do you 'juxtapose' opposites?

Question

I'm confused. I asked about a heiku I was attempting to write and I was told that a common trait of a haiku was 'juxtaposing opposites.' How do you achieve this?

Answer 1

You would have to try to put things together that would contrast their values
An example might be putting together two colours that were different but complimented each other.
Or it could be when someone combines two flavours in a recipe
to bring out a different flavour