The topic of this graduate thesis is to know, understand and apply the chemical basis of living beings, water and biologically important organic molecules in the classroom. The first part of work describes the chemical basis of living beings, which includes water and biologically important organic molecules, such as carbohydrates, lipids, nucleic acids and proteins. The work describes each of these molecules and their role in the functioning of the organism. The second part of the work refers to the introduction of students to knowledge, understanding and application of chemical basis in the classroom through the subject of nature and society. In order to find out the representation of these topics in the classroom, the involvement of these topics in the classroom is analyzed and revealed based on the curriculum for primary school and the curriculum of the subject nature and society for primary school. Since students are introduced to the subjects of chemistry and biology in the upper grades of primary school and in secondary schools, the aim of this work is to practically present the close connection between organic and inorganic matter. The chemical basis, water and biologically important organic molecules make the basis of proper nutrition, so the second part shown separately children's nutrition. Its importance is summed up through the pyramid of proper nutrition. Children are in a period of intense growth and development and it is not possible without proper nutrition. Proper nutrition implies a balanced entry of energy and nutrients. So that children, from an early age, get acquainted with the positive nutritious habits, along the pyramid of proper nutrition, is also shown the energy value to the age of children. Except the energy value, it is also mentioned the presence of biologically important molecules in children's nutrition. They are manifested through the basic ingredients of food: carbohydrates, proteins, fats, vitamins and minerals. Also is shown their recommended part in children's nutrition. An the end is an example menu for one day of a school child, adhering to energy and nutritional values.