(According to Hindu Mythology. These are only the summary versions. I will write up the details in another blog post!)
There is no single but many versions of the story of creation of the Universe in Hinduism. It is up to the people what they want to believe because every version seems convincing to some extent.
But if one really wants to know the truth they must fix up a meeting with Rishi Markandeya because he is the only one who has the privilege to see the creation and destruction of the universe every time. He received a boon from the Devi to watch the whole process. (But there are many stories on exactly who gave him the boon!!)
I will start with the most popular version which is related to Lord Vishnu.
In the beginning that is after the destruction of the universe there was only an ocean, nothing else. Miles and miles of only ocean but was it water? Whatever it was it was liquid in form. And in that ocean suddenly there appeared a baby on a leaf. This was Lord Vishnu. Many versions says the baby was born from Devi. The baby kept floating on a leaf for several days and grew into an adult. Lord Vishnu went to deep meditation for millions and millions of years. He was simply lying down and meditating, learning about the many forms of knowledge with his powers. There was always a calm smile on his face. He was clothed in yellow and had a dark blue skin tone.
While meditating a stem from his navel grew. It was a Lotus stem. It grew up and up and on it was born Lord Brahma. Lord Brahma of the ancient had five heads in total. He was clothed in pearl white garments and had a fairer tone. He was quite surprised with his own creation. He was confused who he was? How he was born? Where from the lotus seat he was sitting on came? There were too many questions (which is obvious!) so he started meditating trying to find answers. He meditated for millions and millions of years but got no clue of his birth. He decided to shrink himself and go down the stem to find the root so he could learn about his birth. He went down for million of years but never could reach an end so he returned back and declared himself the God.
At the same moment, Vishnu appeared before him and introduced himself as his creator as he was born of his navel. Lord Brahma didn’t believe him and there started a debate on who was the real God, who was the most powerful.
When the debate became serious a voice sounded. A long pillar appeared in front of their eyes. The voice came from the pillar. It said whoever would find the end or start of the pillar would be declared the strongest! Thus both Lord Vishnu and Lord Brahma started their journey. Lord Brahma decided to find the start and Lord Vishnu, the end. But both couldn’t find anything, it was just the pillar going on and on. Lord Vishnu realized that there were someone more powerful than them and probably the real God. Lord Brahma however cheated and called the Ketaki flower to come to him. He instructed the flower to support him in lying that he had found it at the start and the flower agreed. When he went back and started narrating of his victory an angry Shiva appeared from the pillar. He cursed the flower and Brahma too!
After that the three went to do their designated job after learning the Knowledge from Devi. Brahma created the universe which we live in, Lord Vishnu is the protector of the universe and Lord Shiva is the destroyer of this universe.
In many places it is written that Lord Brahma simply wished that from one he becomes many and thus many offspring were born from his body. And thus, he is the grandfather of every being in this universe. He is also the creator of the three main places that is : Swarg , Bhu and Naraka which he created from the petals of a magical lotus.
Here the Devi is given the importance. She is the controller and she maintains everything even the Tridevs (Brahma, Vishnu and Shiv).
So, the story goes like this, she gave birth to Lord Vishnu in his baby form with her power. He grew up on the ocean. Lord Brahma was born from his navel. And then she created Madhu and Kaitab from the dirt of Vishnu’s ears. They were the first evil savages one can say, but their birth also had a purpose. They started disturbing Lord Brahma and Lord Vishnu that too on orders of Devi. Lord Brahma was not a fighter so he called for help from Lord Vishnu and Lord Vishnu fought with them for millions and millions of years. Lord Shiva sprung from Lord Vishnu’s forehead to help him. But they were not successful. At the end they asked for Devi’s help and she helped them in killing them. The fat from their bodies turned into land masses on which the creation lives. Later on Lord Brahma continued the process of creation!
Mahakal and Mahakali are the two forces who together gave birth to the whole universe. They have immense powers and using their powers they gave birth to Lord Brahma and Goddess Laxmi, Lord Vishnu and Goddess Parvati and Lord Shiva and Goddess Saraswati. This made them brothers and sisters, like Lord Brahma is Laxmi’s brother. So they married among themselves, Lord Vishnu with Laxmi, Brahma with Saraswati and Shiva with Parvati to help in the creation of the universe.
They learned the knowledge from Mahakal and Mahakali and used them in creation, maintenance and destruction of the universe. Mahakal is said to reside in the body of Lord Shiva so Mahakal is also a form of Lord Shiva, and Mahakali is within Goddess Parvati.
Lord Brahma and Goddess Saraswati together created many creatures and from them continued their generations. From the Saptarishis (Seven rishi sons of Lord Brahma) were born the principle gods and powerful beings. The Devs were children of Rishi Kashyap and Aditi. Likewise, he had many more children from his 13 wives who were the daughter of Prajapati Daksh, who was also a son of Lord Brahma!
There are many more versions and many more stories about the creation of the universe. There is no single event. It is also mentioned that it is not the first time that the universe is created. The universe has been created many times before and may be every-time the process of creation is different. But that is my thinking! In Hinduism, you have the freedom to choose whatever you feel is true. Whatever may be the truth only one knows the answer that is Rishi Markandeya! Hope we find him again to seek the true knowledge from him.