Producing them involves high pressure, heat and hydrogen gas in the presence of a metal catalyst. This process turns liquid vegetable oils into a thick, toxic sludge that is solid at room temperature.
You have to wonder what was going through the head of the person who actually thought of putting this stuff in food and selling it to humans. It is baffling, really.
Of course, trans fats are more than just unappetising. Studies have shown that they are incredibly harmful as well, linked to a drastic increase in heart disease risk