It is said that the universe began with the Big Bang. As the universe was born from the Big Bang, time began to flow, and energy came into existence. It began to expand at the speed of light, becoming the present-day universe. At the point when the early universe began expanding, the age-old question, "Where did energy come from?" can be answered using the mathematical model of the Planck's law and the Planck units. The universe was born from nothing, as empty space with a Planck length. As time began to flow within this space, an unknown energy particle with the Planck mass, which would later be converted to energy, was simultaneously generated. This unknown particle is called the pep (pre-energy particle). As the early universe expanded, peps were continuously generated, producing peps equal to the mass and energy of the present-day universe. The internal temperature of the early universe reached the Planck temperature, 1.41678 × 10^32 K. Now, this space became so hot that the early universe, unable to withstand the Planck temperature, experienced an event called the Big Bang, which began expanding at the speed of light. The Big Bang refers to a phase change where the pep is converted into energy. The Planck temperature is hot spot where energy is generated and annihilated. The generation and annihilation of energy demonstrates that time, energy, and temperature are interrelated. The idea that energy is generated and annihilated does not violate the law of conservation of energy but rather helps us understand the universe.