To a small jar, add oats, chia seeds, flax seeds, and brown sugar, an then top with wet ingredients. Use a small spoon or whisk to stir everything together completely.
1/3 cup old-fashioned oats, 1 tablespoon chia seeds, 1 tablespoon ground flax seeds, 1 teaspoon brown sugar, 1/2 cup Greek yogurt, 1/2 cup milk, 1/2 teaspoon vanilla extract, 1 teaspoon maple syrup
Seal jar with an airtight lid, then refrigerate overnight, or at least for 4 hours.
Give overnight oats a stir before serving, adding a splash more milk if you prefer yours a thinner consistency. Garnish as desired and enjoy!