Starting with milk, fill each jar with ¾ cup milk, ⅓ cup rolled oats, 1 tablespoon raisins, ½ to 1 teaspoon cinnamon (to taste), 1 tablespoon chia seeds, and 1 tablespoon flax seeds. Stir to mix well.
Add ⅓ cup blueberries to each jar, or ½ apple, pared and cut into bite-sized pieces.
Add remaining ¼ cup of milk to each jar to fill. Cover and refrigerate overnight or up to 4 days. Simply stir and eat.