Lapland Packlist: What to pack for your trip to Lapland

It probably won't surprise you, but during winter it can be very cold in Lapland, with temperatures between -10°C and -20°C and even -30°C. The lowest temperatures can be expected between the holidays and mid-February. But this shouldn't be a problem, if you're well prepared for this. The most important is to wear multiple layers and with multiple we don't mean 2 or 3.
But what exactly should you bring to protect yourself against the cold? When traveling with a travel agency they'll probably provide you with a thermal overall, so what if you're organizing this trip yourself?
Here is a list of what should definitely not be missing in your suitcase to Lapland.