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In the beginning, approximately 13.75 billion years ago, there was hydrogen - lots and lots of hydrogen along with a little helium. Objects that have mass attract one another, and hydrogen atoms have mass. So the universe's hydrogen atoms had a tendency to clump together.

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If a large group of hydrogen atoms clump together, there is enough gravitational pressure to create a fusion reactor - a sun. It radiates massive quantities of heat and light into space. It also forms fusion products in its core. Hydrogen atoms fuse together to form helium atoms. Helium atoms fuse to form carbon and so on, forming all the elements up through iron.

Large stars then explode as supernova. These explosions are gigantic and create all of the heavier natural elements up through Uranium. A cloud of dust and debris spreads out across space.

The dust from these supernova explosions collects into new solar systems, like ours. New stars form, with orbiting planets made from the fusion products of former stars. The process repeats.

Let's take one quick tangent here to look at the size of our universe. Stars live in groups that we call galaxies. How many galaxies are there? Current estimates run anywhere from 100 billion to 500 billion. How many is that? Let's assume that a single grain of salt represents one galaxy. Take a one pound (0.45 kg) package of salt and pour it out onto your kitchen table. That little pile contains about 10 million galaxies. There are approximately 10 million grains of salt in a pound. So to get 200 billion grains of salt, we need about 20,000 pounds of salt. That's a dump truck load of salt, or a pile 12 feet wide and 6 feet high. There are a lot of galaxies in our universe.

But galaxies are not as big as a grain of salt. They are monstrous. The milky way galaxy - our galaxy - is 100,000 light years across. There are 200 to 400 billion stars in our one galaxy. Many of those stars have their own planets.

Let's look at one star, our sun. Let's model our sun as an ordinary soccer ball. And here is earth, to scale: It is about 2 millimeters wide - the size of a typical peppercorn. At this scale, Earth the peppercorn resides about 75 feet (24 meters) away from the sun, the soccer ball. That's to scale. Neptune would be a chickpea about half a mile (0.8 km) away from the soccer ball.

The point is that our universe is utterly enormous. Planet earth is a tiny speck that is part of a galaxy which, at the scale of the universe, is a tiny speck itself.

Nonetheless, this tiny speck of a planet - this peppercorn - is us. On this peppercorn we have life. Millions of species form an intricate web of life on planet Earth today. Where did this life come from? Through the processes of abiogenesis and evolution, life arose, life evolved, and today, on this peppercorn, we have us. People. Roughly 7 billion people and rising.

Millions of interlocking pieces of scientific evidence, revealed through several centuries of discovery, paint this amazing picture of our universe. This is how Hydrogen turns into People.