but before Stephen Sillett, no one could see or even imagine the forest in the trees.

Stephen was an explorer of new worlds from the start.

He spent his boyhood in Harrisburg, Pennsylvania

reading Tolkien and playing Dungeons and Dragons with his brother Scott.

But when the Sillett family visited their grandparent's cabin near Gettysburg,

their grandmother Helen Poe Sillett,

would take the boys into the nearby mountains and forests to bird-watch.

They called Grandma Sillett Poe,

and she taught the boys to identify songbirds, plants and even lichens,

creatures that often look like splotches of carpet glued to the shady sides of rocks and tree trunks.

Looking upwards, both boys found their callings.

Scott became a research scientist specializing in migratory birds.

Stephen was more interested in the trees.

The tangle of branches and leaves attracted his curiosity.

What could be hidden up there?

By the time Stephen was in college, that curiosity pulled him skyward

to the tallest trees on Earth: the ancient coast redwoods of Northern California.

Rising from trunks up to 20 feet in diameter,

redwoods can grow up to 380 feet, or 38 stories, over a 2,000 year lifetime.

But no one had thought to investigate the crowns of these natural skyscrapers.

Were there more than just branches up there?

Stephen decided to find out firsthand.

In 1987, Stephen, his brother Scott and his friend Marwood

drove from Reed College in Oregon

to Prairie Creek Redwoods State Park in Northern California.

Deep inside the park, Stephen picked the tallest redwood he could find.

Its lowest branches were almost 100 feet up,

far beyond his reach.

But he saw a younger, shorter redwood growing next to the target tree.

With a running start, he leapt and grabbed the lowest branch,

pulled himself up and scurried upwards.

He was free climbing without ropes or a harness,

one misstep meant death.

But up he went, and when he reached the peak,

he swayed and leapt across the gap of space onto a branch of the target tree

and into a world never seen before.

His buddy Marwood followed him up,

and the two young men free climbed high into the redwood's crown.

Stephen came across lichens like Grandma Poe had shown him as a boy.

He noticed that the higher he went, the thicker the branches were,

not the case with most trees.

He found moist mats of soil many inches thick,

made from fallen needles, bark, other plant debris and dust from the sky

piled on the tops of the large branches.

He even found reiterations:

new redwood tree trunks growing out from the main trunk.

The redwood had cloned itself.

When Stephen reached the pinnacle,

he rested on a platform of crisscrossing branches and needles.

Growing in the soil mat was a huckleberry bush with ripe berries!

He ate some and waited for his friend.

Stephen had discovered a new world hundreds of feet above the ground.

His climb led to more excursions, with safety equipment, thank goodness,

up other ancient redwoods as he mapped and measured the architecture

of branches and additional trunks in the canopy of an entire grove.

Stephen became an expert in the ecology of the tallest trees on Earth

and the rich diversity of life in their crowns, aerial ecosystems no one had imagined.

There are ferns, fungi and epiphytic trees normally found at ground level

like Douglas firs, hemlocks and tan oaks

whose roots had taken hold in the rich wet soil mats.

Invertebrates such as ants, bumblebees, mites, beetles, earthworms and aquatic crustacean copepods

make their homes alongside flowering plants like

rhododendrons, currant and elderberry bushes.

Ospreys, spotted owls, and jays search the canopy for food.

Even the marbled murrelet, a Pacific seabird,

flies many miles from the ocean to nest there.

Squirrels and voles peek out of penthouse burrows.

And the top predator? The mighty wandering salamander!

Sillett's research has changed how we think about tall trees,

and bolstered the case for their conservation,

not just as impressive individual organisms

but as homes to countless other species.

So when you look up into the branches and leaves of a tree,

ask, "What else is up there?"

A new world might be just out of reach. So leap for it.