01 -  Preheat oven to 375°F (190°C). Line a 12-cup muffin tin with paper liners or lightly grease with nonstick spray. 
 02 -  In a large mixing bowl, whisk together flour, cornmeal, sugar, baking powder, and salt until uniform. 
 03 -  In another bowl, whisk together milk, eggs, melted butter, and vanilla extract until fully blended. 
 04 -  Pour wet ingredients into dry mixture and stir gently with a spatula until just combined. Avoid overmixing. 
 05 -  Gently fold rainbow sprinkles into the batter until evenly distributed. 
 06 -  Divide batter evenly into prepared muffin tin, filling each cup about three-quarters full. 
 07 -  Bake for 16 to 18 minutes, or until a toothpick inserted into the center comes out clean. 
 08 -  Let muffins cool in the pan for 5 minutes, then transfer to a wire rack until completely cool.