As stated before, kṣetra is the field of activities, and there are two kinds of kṣetra-jña: the individual living entity and the supreme living entity. As stated in the Taittirīya Upaniṣad (2.5), brahma pucchaṁ pratiṣṭhā. There is a manifestation of the Supreme Lord's energy known as anna-maya, dependence upon food for existence. This is a materialistic realization of the Supreme. Then, in prāṇa-maya, after realizing the Supreme Absolute Truth in food, one can realize the Absolute Truth in the living symptoms or life forms. In jñāna-maya, realization extends beyond the living symptoms to the point of thinking, feeling and willing. Then there is Brahman realization, called vijñāna-maya, in which the living entity's mind and life symptoms are distinguished from the living entity himself. The next and supreme stage is ānanda-maya, realization of the all-blissful nature. Thus there are five stages of Brahman realization, which are called brahma puccham. Out of these, the first three—anna-maya, prāṇa-maya and jñāna-maya—involve the fields of activities of the living entities. Transcendental to all these fields of activities is the Supreme Lord, who is called ānanda-maya. The Vedānta-sūtra also describes the Supreme by saying, ānanda-mayo 'bhyāsāt: the Supreme Personality of Godhead is by nature full of joy. To enjoy His transcendental bliss, He expands into vijñāna-maya, prāṇa-maya, jñāna-maya and anna-maya. In the field of activities the living entity is considered to be the enjoyer, and different from him is the ānanda-maya. That means that if the living entity decides to enjoy in dovetailing himself with the ānanda-maya, then he becomes perfect. This is the real picture of the Supreme Lord as the supreme knower of the field, the living entity as the subordinate knower, and the nature of the field of activities. One has to search for this truth in the Vedānta-sūtra, or Brahma-sūtra.
(Bhagavad-Gita----13:5----purport).

As stated in the Taittirīya Upaniṣad (2.9), brahma pucchaṁ pratiṣṭhā. There is a manifestation of the Supreme Lord's energy known as anna-maya, dependence upon food for existence. This is a materialistic realization of the Supreme. Then, inprāṇa-maya, after realizing the Supreme Absolute Truth in food, one can realize the Absolute Truth in the living symptoms or life forms. In jñāna-maya, realization extends beyond the living symptoms to the point of thinking, feeling and willing. Then there is Brahman realization, called vijñāna-maya, in which the living entity's mind and life symptoms are distinguished from the living entity himself. The next and supreme stage is ānanda-maya, realization of the all-blissful nature. Thus there are five stages of Brahman realization, which are called brahma puccham. Out of these, the first three—anna-maya, prāṇa-maya and jñāna-maya—involve the fields of activities of the living entities. Transcendental to all these fields of activities is the Supreme Lord, who is called ānanda-maya. The Vedānta-sūtra also describes the Supreme by saying, ānanda-mayo 'bhyāsāt: the Supreme Personality of Godhead is by nature full of joy. To enjoy His transcendental bliss, He expands into vijñāna-maya, prāṇa-maya, jñāna-maya and anna-maya.
(Bhagavad-Gita----13:5----purport).

There are various stages of elevation the jīva goes through, which are like different shells (koṣas) covering him. They are the coverings of food (anna-maya), life air (prāṇa-maya), mind (mano-maya, or jñāna-maya), and transcendental knowledge (vijñāna-maya). When the final shell is penetrated, the soul attains pure consciousness, enters the state of complete bliss (ānanda-maya), and experiences sac-cid-ānanda as universal.
(Renunciation Through Wisdom).

Within the body there are five different departments of existence, known as anna-maya, prāṇa-maya, mano-maya, vijñāna-maya and, at last, ānanda-maya. In the beginning of life, every living entity is food conscious. A child or an animal is satisfied only by getting nice food. This stage of consciousness, in which the goal is to eat sumptuously, is called anna-maya. Anna means "food." After this one lives in the consciousness of being alive. If one can continue his life without being attacked or destroyed, one thinks himself happy. This stage is called prāṇa-maya, or consciousness of one's existence. After this stage, when one is situated on the mental platform, his consciousness is called mano-maya. The materialistic civilization is primarily situated in these three stages, anna-maya, prāṇa-maya and mano-maya. The first concern of civilized persons is economic development, the next concern is defense against being annihilated, and the next consciousness is mental speculation, the philosophical approach to the values of life.
(Krsna Book).

As it is said in the Vedānta-sūtra, ānanda-mayo ’bhyāsāt. The Supreme Brahman and the subordinate Brahman, or the Supreme Personality of Godhead and the living entities, are both joyful by nature. As long as the living entities are situated in the lower four stages of life— anna-maya, prāṇa-maya, mano-maya and vijñāna-maya—they are considered to be in the material condition of life, but as soon as one reaches the stage of ānanda-maya, he is a liberated soul. This ānanda-maya stage is explained in the Bhagavad-gītā as the brahma-bhūta (S.B.4:30:20) stage. There it is said that in the brahma-bhūta stage of life there is no anxiety and no hankering. This stage begins when one is equally disposed toward all living entities, and it then expands to the stage of Kṛṣṇa consciousness, in which one always hankers to render service unto the Supreme Personality of Godhead. This hankering for advancement in devotional service is not the same as hankering for sense gratification in material existence. In other words, hankering remains in spiritual life, but it becomes purified. Similarly, when our senses are purified, they are freed from all material stages, namely anna-maya, prāṇa-maya, mano-maya and vijñāna-maya, and they become situated in the highest stage—ānanda-maya, or blissful life in Kṛṣṇa consciousness.
(Krsna Book).

The cosmic manifestation has been made possible because of the entrance of the Supreme Personality of Godhead as Mahā-Viṣṇu within this material world. The total material energy is agitated by the glance of Mahā-Viṣṇu, and only then does the interaction of the three material qualities begin. Therefore it should be concluded that whatever material facilities we are trying to enjoy are available only due to the mercy of the Supreme Personality of Godhead.
Within the body there are five different departments of existence, known as anna-maya, prāṇa-maya, mano-maya, vijñāna-maya and, at last, ānanda-maya. In the beginning of life, every living entity is food conscious. A child or an animal is satisfied only by getting nice food. This stage of consciousness, in which the goal is to eat sumptuously, is called anna-maya. Anna means "food." After this one lives in the consciousness of being alive. If one can continue his life without being attacked or destroyed, one thinks himself happy. This stage is called prāṇa-maya, or consciousness of one's existence. After this stage, when one is situated on the mental platform, his consciousness is called mano-maya. The materialistic civilization is primarily situated in these three stages, anna-maya, prāṇa-maya and mano-maya. The first concern of civilized persons is economic development, the next concern is defense against being annihilated, and the next consciousness is mental speculation, the philosophical approach to the values of life.
If by the evolutionary process of philosophical life one happens to reach the platform of intellectual life and understands that he is not this material body but a spiritual soul, he is situated in the vijñāna-maya stage. Then, by evolution in spiritual life, he comes to the understanding of the Supreme Lord, or the Supreme Soul. When one develops his relationship with Him and executes devotional service, that stage of life is called Kṛṣṇa consciousness, the ānanda-maya stage. Ānanda-maya is the blissful life of knowledge and eternity. As it is said in the Vedānta-sūtra, ānanda-mayo ’bhyāsāt. The Supreme Brahman and the subordinate Brahman, or the Supreme Personality of Godhead and the living entities, are both joyful by nature. As long as the living entities are situated in the lower four stages of life— anna-maya, prāṇa-maya, mano-maya and vijñāna-maya—they are considered to be in the material condition of life, but as soon as one reaches the stage of ānanda-maya, he is a liberated soul. This ānanda-maya stage is explained in the Bhagavad-gītā as the brahma-bhūta (S.B.4:30:20) stage. There it is said that in the brahma-bhūta stage of life there is no anxiety and no hankering. This stage begins when one is equally disposed toward all living entities, and it then expands to the stage of Kṛṣṇa consciousness, in which one always hankers to render service unto the Supreme Personality of Godhead. This hankering for advancement in devotional service is not the same as hankering for sense gratification in material existence. In other words, hankering remains in spiritual life, but it becomes purified. Similarly, when our senses are purified, they are freed from all material stages, namely anna-maya, prāṇa-maya, mano-maya and vijñāna-maya, and they become situated in the highest stage—ānanda-maya, or blissful life in Kṛṣṇa consciousness. The Māyāvādī philosophers consider ānanda-maya to be the state of being merged in the Supreme. To them, ānanda-maya means that the Supersoul and the individual soul become one. But the real fact is that oneness does not mean merging into the Supreme and losing one's own individual existence. Merging into the spiritual existence is the living entity's realization of qualitative oneness with the Supreme Lord in His aspects of eternity and knowledge. But the actual ānanda-maya (blissful) stage is attained when one is engaged in devotional service. That is confirmed in the Bhagavad-gītā: mad-bhaktiṁ labhate parām (B.G.18:54). Here Lord Kṛṣṇa states that the brahma-bhūta ānanda-maya stage is complete only when there is an exchange of love between the Supreme and the subordinate living entities. Unless one comes to this ānanda-maya stage, his breathing is like the breathing of a bellows in a blacksmith's shop, his duration of life is like that of a tree, and he is no better than the lower animals like the camels, hogs and dogs.
Undoubtedly the eternal living entity cannot be annihilated at any point. But the lower species of life exist in a miserable condition, whereas one who is engaged in the devotional service of the Supreme Lord is situated in the pleasurable, or ānanda-maya, status of life. The different stages described above are all in relationship with the Supreme Personality of Godhead. Although in all circumstances there exist both the Supreme Personality of Godhead and the living entities, the difference is that the Supreme Personality of Godhead always exists in the ānanda-maya stage, whereas the subordinate living entities, because of their minute position as fragmental portions of the Supreme Lord, are prone to fall to the other stages of life. Although in all the stages both the Supreme Lord and the living entities exist, the Supreme Personality of Godhead is always transcendental to our concept of life, whether we are in bondage or in liberation. The whole cosmic manifestation becomes possible by the grace of the Supreme Lord, it exists by the grace of the Supreme Lord, and when annihilated it merges into the existence of the Supreme Lord. As such, the Supreme Lord is the supreme existence, the cause of all causes. Therefore the conclusion is that without development of Kṛṣṇa consciousness one's life is simply a waste of time.
For those who are very materialistic and cannot understand the situation of the spiritual world, the abode of Kṛṣṇa, great sages have recommended the yogic process whereby one gradually rises from meditation on the abdomen, which is called mūlādhāra or maṇipūraka meditation. Mūlādhāra and maṇipūraka are technical terms which refer to the intestines within the abdomen. Grossly materialistic persons think that economic development is of foremost importance because they are under the impression that a living entity exists only by eating. Such grossly materialistic persons forget that although we may eat as much as we like, if the food is not digested it produces the troubles of indigestion and acidity. Therefore, eating is not in itself the cause of the vital energy of life. For digestion of eatables we have to take shelter of another, superior energy, which is mentioned in the Bhagavad-gītā as vaiśvānara. Lord Kṛṣṇa says in the Bhagavad-gītā that He helps the digestion in the form of vaiśvānara. The Supreme Personality of Godhead is all-pervasive; therefore, His presence in the stomach as vaiśvānara is not extraordinary.
(Krsna Book).