Pet owners are growing increasingly interested in understanding the ingredients in cat and dog food to make informed decisions about their pets' nutrition. To support this interest, the Cornell Animal Science website will provide information beyond what is covered in this article, utilizing well-researched and credible sources. The project aims to educate pet owners, helping them confidently navigate the evolving landscape of pet food ingredient options. Chapter 1 examines the use of animal products in pet food, beginning with clarifying the origins of animals used in foods and addressing the sustainability and nutritional safety of animal byproducts. Definitions of raw and rendered animal products according to AAFCO guidelines are provided, including a distinction between raw ingredients and raw products. This chapter also includes examples of raw and rendered animal products and byproducts as they appear in real ingredient lists and offers a nutrient comparison to further illustrate their benefits in pet food. Chapter 2 explores the factors driving the increasing popularity of grain-free diets. It clarifies the primary allergens commonly found in cats and dogs, categorizes the carbohydrate sources in pet foods, and offers examples of grain-free and grain-inclusive labels. This chapter also discusses the functional benefits of cereal and pulse grains, and tuber vegetables. In a rapidly evolving pet food market, where the misconception of animal byproducts and grain-free diets are increasingly shaping consumer choices, this project serves as a resource for pet owners to make well-informed decisions by bridging the understanding of ingredient sources and their roles in pet food.