Car will not start in extreme low temp

I am no expert but three things occur to me: 1) battery 2) gas 3) oil. First, there may be moisture in the gas due to condensation. Moisture is a natural byproduct of combustion. There are products that can help this. Google knows all. Second, batteries - if your battery is old or (frankly) cheap - i.e. lacking in "cold cranking amps" - cold weather will render it useless. And in "extreme low temperatures" - here's a true story. One time here in Kansas City we had below zero temperatures for what seemed like weeks. I remember that it was zero on Christmas day and everyone was joking about the heat wave. Anyway, for anyone to keep their car starting, they either had to have a well-heated garage or they had to go out and start their car every few hours. Me, I took extreme measures. Whenever I parked for any length of time, I took the battery out of my car and brought it inside with me. It was a pain but at least it kept me sleeping sleep through the night. And as for oil: In cold temps, oil can become extremely viscous - i.e. thick. This hinders starting because oily sludge keeps parts from cranking over. In Alaska and other very cold places, they put plug-in oil heaters into the engine in place of the dip stick. If you have a plug near where you keep your car, try this. There are a lot of other things that can cause your problem, I suppose, but these are relatively simple things I would try before taking the car to the shop.