The restaurant is trying to attract more customers, and the new menu is an important 'piece of the puzzle'. [=an important part of what is being done]
Ecologists no longer view different species as independent, but instead see them as pieces of the same 'jigsaw puzzle'.
His strange behavior is a 'puzzle' to his friends. [=his friends don't understand the reason for his strange behavior]
(..) I think this is the place. - Fill these out. - Thank you. We'll be right back. Oh,take your time. I'll just finish my crossword puzzle. Oh,wait. Leonard,I don't think I can do this. What,are you kidding? You're a semi-pro. No. We are committing genetic fraud. (..)2007 TvShow: The Big Bang Theory Title: Pilot Season: 1 Episode 1