SB 2.8.16

pramāṇam aṇḍa-kośasya
 bāhyābhyantara-bhedataḥ
mahatāṁ cānucaritaṁ
 varṇāśrama-viniścayaḥ
Synonyms: 
pramāṇam — extent and measurement; aṇḍa-kośasya — of the universe; bāhya — outer space; abhyantara — inner space; bhedataḥ — by division of; mahatām — of the great souls; ca — also; anucaritam — character and activities; varṇa — castes; āśrama — orders of life; viniścayaḥ — specifically describe.
Translation: 
Also, please describe the inner and outer space of the universe by specific divisions, as well as the character and activities of the great souls, and also the characteristics of the different classifications of the castes and orders of social life.
Purport: 

Mahārāja Parīkṣit is a typical devotee of Lord Kṛṣṇa, and as such, he is anxious to know the complete significance of the creation of the Lord. He wants to know the inner and outer space of the universal form. It is quite fitting for the real searcher of knowledge to know all about this. Those who are of the opinion that the devotees of the Lord are satisfied with mere sentiments can find in the inquiries of Mahārāja Parīkṣit good lessons as to how inquisitive a pure devotee is to know things in their true perfection. The modern scientist is unable to know about the inner space of the universal horizon, and what to speak of the space which covers the universe.

Mahārāja Parīkṣit is not satisfied with only material knowledge. He is inquisitive about the character and activities of the great souls, the devotees of the Lord. The glories of the Lord and the glories of His devotees, combined together, comprise the complete knowledge of Śrīmad-Bhāgavatam. Lord Kṛṣṇa showed His mother the complete universal creation within His mouth, while she, completely charmed by her son, wanted to look inside the mouth of the Lord just to see how much earth the child had eaten. By the grace of the Lord the devotees are able to see everything in the universe within the mouth of the Lord.

The very idea of the scientific divisions of four classes of human society and four orders of life is also inquired about herewith on the basis of individual personal quality. The four divisions are exactly like the four divisions of one’s personal body. The parts and parcels of the body are nondifferent from the body, but by themselves they are only parts. That is the significance of the whole scientific system of four castes and four social orders. The value of such scientific divisions of human society can be ascertained only in terms of the proportionate development of devotional service to the Lord. Any person employed in government service, including the president, is a part and parcel of the entire government. Everyone is a government servant, but no one is the government himself. That is the position of all living entities in the government of the Supreme Lord. No one can artificially claim the supreme position of the Lord, but everyone is meant to serve the purpose of the supreme whole.