Add the desired amounts of milk, oats, yogurt, chia seeds and banana to a jar or container and give them a good stir. Refrigerate overnight or for at least 5 hours.
In the morning, add additional liquid if you'd like. Once you achieve the desired consistency, top with fruit, nuts, nut butter, seeds, protein powder, granola, coconut, spices, zest or vanilla extract.
The mixture will keep for up to 2 days. If you don't add the banana, up to 4 days. However, once you are experienced, you'll have no problem whipping up another batch midweek if needed!