|Xuất hiện lần đầu||Harry Potter and the Prisoner of Azkaban|
A Shrinking Solution is a potion which shrinks living things by apparently causing them to revert to childhood.
Professor Snape has Harry's Potions class make Shrinking Solution. Draco is, at the time, malingering with the wound inflicted by Buckbeak, and Snape has Harry and Ron prepare ingredients for him. A somewhat comic side note is caused by Neville's attempt to create this potion, and Hermione's setting him right.
Ingredients mentioned are peeled Shrivelfigs, very evenly diced daisy roots, leech juice, and sliced caterpillars.
While we do see the effect of the potion when it is applied to Neville's toad, Trevor, the non-entertainment use and application of this potion is never explained. We imagine it might be useful for removing trees and the like – dose the oak until it is a sapling, then simply uproot it.
The episode where the potion is being made is meant more as a highlight on the characters involved, and specifically as a chance for Draco to be close enough to Harry, for long enough, to needle Harry about Sirius Black. Supervision, preferably by Snape, is necessary, to prevent Harry from simply walking away from the hated Draco. The episode also is used to highlight Neville's humorous incompetence with the cauldron; Snape's ongoing dislike of Harry and Gryffindor house, and partiality towards his own House; Hermione's book knowledge and how she is applying it; Draco's sly personality; and Harry and Ron's steadfastness in the face of adversity.