How to find Strings in linux directory

To find some string in a directory you can find a String in this way:

ps aux | grep stringToFind

Example, you have a directory called Fruit, which contains all kind of files with fruits. You need to search the file/s containing the word "Apple"

you go to Fruit directory:
cd /home/username/Fruit

then you search for the word Apple in all subdirectory:
ps aux | grep Apple *
ps aux | grep Apple */*
ps aux | grep Apple */*/*
 
... and so on till you have this indication:

grep: No match.

This means that you don't have any more subdirectories to explore

Up to know I use this command because is the simplest one.