system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How come fruit like pears/plums/peaches etc go from hard to juicy. Where was the juice all that time?
gpt
The juice is always there, however the cells that make up the fruit are “turgid” which means they have the liquid absorbed inside them and become like a balloon filled up with air(makes fruit “hard”).
 As more of the cells die(when the fruit gets older and left out)  they cannot hold the liquid as well so it leaks and the fruit becomes juicy with cells becoming “softer” (like a ballon with less air in it) as the juice moves in between cells and does not stay inside the cells.
Basically the reason is that there is always water in between the cells, which evaporates, cells die, and as the juice wants to equal out between the cells and outside the cells(but still in the fruit), fruit gets more juicy. This is why when you bite into a hard fruit, the juice releases, but a soft fruit already has most of the juice in between the cells.
 Edit added ballon analogy.