Position a rack in the center of the oven and preheat oven to 400 degrees Fahrenheit. Lightly coat 24 nonstick miniature muffin cups with cooking oil spray.
In a medium bowl, combine bran, flour, flaxseed, baking soda, cinnamon, and salt. Set aside. In another medium bowl or in a blender, combine the milk, honey, banana, egg, olive oil, and vanilla extract until smooth.
Make a well in the center of the dry ingredients, and pour in one-third of the liquid mixture. Using a spoon, stir until smooth. Add remaining liquid mixture and stir just until combined. Add blueberries and stir again, but do not over mix.
Spoon 2 tablespoons of batter into each prepared muffin cup. Bake about 8 minutes, or until the tops spring back when pressed gently in the centers. Do not overbake. Cool in the pan on a wire rack for 10 minutes before removing from the cups. Serve warm or cool completely on the rack.