Desserts can be simple or intricate and include pastries, pies, meringues and custards. Common dessert ingredients are eggs, flour, sugar, and butter or oil, with some requiring additional liquids or leavening agents. Popular flavorings include dried, candied or fresh fruit, nuts, cocoa or spices. Cakes are often filled or iced and can be decorated. Birthday cakes are traditionally served on celebratory occasions and come in various recipes, some being bread-like while others are more rich or intricate. Cake making has become easier over time with baking devices and instructions helping novices prepare cakes.