Similarly, one who wants to concentrate on the teachings of Upanishads only, without going through the process of cooking, is like one trying to have a fruit, without having to go through the stages of flowers, cross pollination, then a raw fruit, and finally a ripe fruit (different stages of Pakvam). Each stage is inevitable and one cannot reach a higher level without passing through the lower stage. There is indeed a preparation and interplay between the Samhitas and Upanishads. For example, many important suktas like Naasaatiya Suktam, Purusha Suktam, trayambaka Mantram, etc are chanted in the Samhita part of the Vedas and not in the Upanishads. Similarly, some rituals like "naachiketaagni" etc are mentioned only in the Upanishads and not in the Samhitai.