You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.

Category: EARLY ART 
Clue: This art form of setting stones or glass into mortar was the main decorative art of the Byzantine Empire
mosaic

Category: PICTURES AT AN EXHIBITION 
Clue: His 1960s works include "I Know How You Must Feel, Brad!" & "As I Opened Fire..."
roy lichtenstein

Category: ELLE 
Clue: Singer & actress Vanessa Paradis has borne this American actor a daughter, Lily Rose Melody

johnny depp