Key lime pie is a essert made of key lime juice, egg yolks, and sweetened condensed milk in a pie crust. The authentic pie is topped with meringue and baked until the meringue is a golden brown. Some key lime pies use other types of whipped toppings or none at all. The dish is named after the small key limes (Citrus aurantifolia 'Swingle') that are naturalized throughout the Florida Keys. Their thorns make them less tractable, their thin yellow rind makes them more perishable, but they are more tart and aromatic than the common Persian limes seen year round in most U.S. grocery stores.