in a nutshell

Example: “In a nutshell, we need more money and more time.”

Origin: Traceable to a specific claim in Pliny the Elder's Natural History, written in the first century AD, which reports that a copy of Homer's Iliad had been produced on parchment small enough to be enclosed in a walnut shell. Whether or not this was true, the story was repeated for centuries as the standard illustration of extreme compression — cited by medieval and Renaissance writers as the limiting case of how much could be fitted into how little — and it is the direct ancestor of the English idiom. The specificity matters: the phrase does not merely mean briefly, but implies that something large has been reduced without being cut down, which is exactly the marvel Pliny was reporting.