Trans-fats are made through a hydrogenation process that turns vegetable oils into solid fats. This document provides historical context on trans-fats, discussing their invention and marketing by Procter & Gamble in the early 20th century. It then summarizes numerous studies that have found relationships between trans-fat consumption and increased health risks such as heart disease, diabetes, and inflammation. Recent actions to reduce trans-fats include bans in some jurisdictions and the FDA moving to limit their use in foods.