Isavasya Upanishad

Isavasya Upanishad is a small Upanishad which does not go into ontological complexities as the Mandukya Upanishad does, but goes into the question of ideal human life. The origins of the concepts of karma yoga, meditations and bhakti yoga, which we see later in the Bhagavad Gita, can be found here. It also tells about the nature of Supreme Reality.