In the first few skandas of Bhagavatamit the answer to your question is explained.

I have recorded the Original Bhagavatam (moolam) discourses. Please listen to them. The answer to this question is contained in elaborate detail there. It is however a very tough subject to understand. 1000 percent tough. You will have to listen repeatedly to the discourses in order to grasp the matter. The entire detail of how creation commenced, the process of creation, all the calculations relating to it and other relavant details are is explained in these Bhagavatam discourses. Such is the level of difficulty in grasping it that people will satisfy themselves saying that Guru Gita is enough and that it grants everything. The beginning of Bhagavatam is very tough to understand. Most people are happy with reading Dasama Skanda which explains the stories of Krishna.

Slokas of Bhagavatam are tough to pronounce. Bhagavatam explains about Self (atma). Bhagavatam is nothing but science. Many eons ago they explained all this science. Lava, volcano, tsunami, future of the earth, birth of the earth, creation of living beings, creation of Indra, and other gods, creation of the deities of the directions, the dimensions of this universe etc. are covered therein. Head will break if you read.

In one or two days you cannot understand. Bhagavatam. Daily you must listen. One day you will understand. That is Moksha (liberation).