Macarons are filled with a variety of fillings, sweet (vanilla filling, fruit filling, etc.), sour (berry, lemon, passion fruit, etc.), salty (cheese, certain nuts, caviar, salmon, etc.), and spicy (jalapeno pepper filling), just like life, it is colorful. The filling is more important than the macaron shell, it gives the macaron its soul, and how good the filling is directly determines how good the macaron is.

("Decorative materials" from "Paris food style handmade macarons and French puffs" )