The universe! The vast expanse that contains all matter, energy, space, and time. Here's an overview:

*Age: Approximately 13.8 billion years old

*Size: Estimated to be around 93 billion light-years in diameter

*Composition:

```+ Ordinary matter: 5%

+ Dark matter: 27%

+ Dark energy: 68%

```

*Structure:

```+ Galaxies: Billions of galaxies, each containing billions of stars

+ Galaxy clusters: Galaxies grouped together by gravity

+ Superclusters: Larger regions of galaxy clusters

```

*Evolution:

```+ Big Bang: The universe began as a singularity, expanding rapidly around 13.8 billion years ago

+ Cosmic inflation: A rapid expansion phase in the early universe

+ Star and galaxy formation: Gravity formed stars and galaxies from the universe's matter

```

*Notable features:

```+ Black holes: Regions with such strong gravity that nothing escapes

+ Dark matter and dark energy: Mysterious components that shape the universe's evolution

+ Cosmic microwave background radiation: The universe's residual heat from the Big Bang

```

*Theories and mysteries:

```+ The origin of the universe's matter-antimatter asymmetry

+ The nature of dark matter and dark energy

+ The possibility of a multiverse

```

*Exploration:

```+ Telescopes: Allow us to study the universe's light and radiation

+ Spacecraft: Enable us to explore our solar system and beyond

+ Simulations: Help us model and understand the universe's behavior

```

Remember, the universe is vast and complex, and our understanding is constantly evolving. There's still so much to discover and explore!