old fashioned rolled oats (not instant, quick, or steel-cut)
Greek yogurt (regular yogurt is thinner; if you use it, you'll need to reduce the amount of milk); read my post for easy instructions for straining regular yogurt to make Greek yogurt.
milk (I used skim, but any kind will work)
chia seeds; I bought mine at Whole Foods; also available on Amazon
half pint (1 cup) mason jars, find them at Walmart and grocery stores; also available on Amazon