Regarding finding the number of unique elements in a list.

Hi, I am newbie at Haskell. I am not able to write a program to find the number of unique elments in a list in haskell. I am also not able to write a porgram to find the elements in the innermost list in a list within lists. Can anybody guide me as to g\how to go about it or better still send me the program. It would be of great help. Have a good day.. cheers, amrit. peace....