I was reading about Modal jazz and there are scales within scales.

Like A minor is in C major. It's a mode but it's the only one I know so I can't give other examples. But what other scales are their inside the Major scale (Please refer to their Relativity to C major to avoid confusion). The scales do not need all the notes of the scale.

A good example would be C major pentatonic.
C, D, E, G, A.

dorian, phrygian, lydian, mixolydian, aolean, locrian are the first that come to mind for every scale.

If you think of a scale as a collection of notes rather than a line of notes this all becomes a little more workable. In other words the 'C' scale is C D E F G A B. From that collection of notes you can have D E F G A B C etc etc. You can add to that collection or subtract whatever notes you want, and start on whatever note you want to construct whatever sound (scale) that you want. There are literally hundreds of scales and of course there are lots of different names for them.

Check out www.jazzbooks.com to find how jazz people deal with this, and to get some good information about how to use them.