Chocolate stains are among the hardest to remove, yet it’s not cocoa itself that latches onto clothes, according to food chemist Chang Y. Lee of Cornell University, but the colored compounds in chocolate dissolved in fat. The best solution is detergent, because it contains complex molecules called surfactants, which have a hydrophilic (water-loving) head and a hydrophobic (water-hating) tail. One part of chocolate’s compound is attracted to water and repels oil, while the other part repels water and is attracted to oil. When the detergent is mixed with water, the hydrophobic tails attach themselves to the grease and pull it away from the clothing.