E101, also known as riboflavin, is a water-soluble vitamin that plays a crucial role in energy production and the metabolism of fats, drugs, and steroids. It is part of the B-vitamin complex and is essential for maintaining healthy skin, eyes, and nerve functions. E101 is commonly found in foods such as eggs, green leafy vegetables, nuts, and dairy products. It is also used as a food additive, providing a yellow color to various products. Adequate intake of E101 is important for overall health and well-being.