ereal grains are used as a staple food all over the world and play a significant role in satisfying the daily dietary and nutritional requirements of the body. They have attracted great nutritional attention due to their easy availability and multiple health benefits for humans. Owing to health-friendly chemical composition, these grains are cultivated everywhere in the world, covering about 60% of cultivated land. The main purpose of this chapter is to provide insight into the chemical composition of cereal grains. Generally, the chemical composition is reviewed in two broad aspects, structural and nutritional composition. Structurally, they are divided into three main parts: bran, endosperm, and germ. The chemical composition of these cereal grains is discussed here in detail. Furthermore, recent research on the main nutritional components of these grains, like carbohydrates, proteins, lipids, vitamins, minerals, and dietary fiber, is examined in this chapter. Bioactive substances like polyphenols, terpenes, alkaloids, and saponins are also present in cereal grains and have significant health effects on the human body. This chapter elucidates that factors like milling, environmental factors (light, water, soil, and temperature), cereal crop varieties, and post-harvest storage period mainly affect the chemical composition. Last, recent approaches to achieve better chemical composition are reviewed. © 2023 selection and editorial matter, Gulzar Ahmad Nayik, Tabussam Tufail, Faqir Muhammad Anjum, and Mohammad Javed Ansari; individual chapters, the contributors.