Explain Why a Smell Can Bring Back a Decade-Old Memory in Seconds

A smell walks past you, cut grass, a specific soap, a school corridor, and suddenly you are eleven again, feeling it as much as remembering it. This explains the actual route a smell takes to the brain's memory centres, and why that link skips the delay every other sense seems to have.

Explain, in plain and slightly fascinating terms, why a specific smell, [describe the smell: cut grass, a particular perfume, a school corridor], can pull up a memory from years ago faster and more vividly than a photo or a song can. Cover the basic route the smell takes to the brain's memory centres, why this link seems to skip the usual delay other senses have, and why the memory that comes back often carries the feeling of that time as strongly as the details. Keep it to two or three short paragraphs, plain English, no unexplained jargon.