The Sun, like all stars, goes through a series of stages in its life cycle. While we are currently in the "main sequence" stage, here's a breakdown of the Sun's past, present, and future:

Past:

* Nebula: The Sun began as a giant cloud of gas and dust called a nebula. This cloud was mostly hydrogen and helium, with traces of heavier elements.

* Protostar: Gravity caused the nebula to collapse, becoming denser and hotter. This created a protostar, a spinning, glowing ball of gas. The protostar continued to grow and heat up for millions of years.

Present:

* Main Sequence: This is the stage the Sun is in now. It has been in this stage for about 4.5 billion years, and will continue for another 5 billion years. During this stage, the Sun fuses hydrogen into helium in its core. This fusion process releases a tremendous amount of energy, which makes the Sun shine.

Future:

* Red Giant: As the Sun runs out of hydrogen in its core, it will start to fuse helium into heavier elements. This process causes the Sun to swell into a red giant, engulfing Mercury, Venus, and potentially Earth.

* Planetary Nebula: After the red giant phase, the Sun will shed its outer layers, creating a planetary nebula – a beautiful, expanding shell of gas.

* White Dwarf: The remaining core of the Sun, a dense ball of carbon and oxygen, will become a white dwarf. This stage is very long-lasting and the white dwarf will slowly cool down over billions of years.

Important Note: These stages are estimates, and variations in the Sun's exact lifespan and future are possible.

Here's a simplified timeline:

* Nebula and protostar: ~50 million years

* Main sequence: ~10 billion years (current stage)

* Red giant: ~1 billion years

* Planetary nebula: ~10,000 years

* White dwarf: ~trillions of years

The Sun's life cycle is a fascinating journey that provides insights into the evolution of stars and the universe itself.