When Jeff Lawson stepped down as CEO of Twilio in 2024, he left behind one of the companies that powers much of the modern internet. Twilio had transformed telecommunications infrastructure into programmable software, allowing developers to embed messaging, voice, and authentication directly into digital products with only a few lines of code. Over time, the platform became deeply embedded in the architecture of the web, supporting everything from ride-sharing services and food delivery apps to healthcare platforms and financial systems.

After more than a decade leading the company he co-founded, Lawson could easily have moved into the quieter phase that often follows the successful run of a public-company founder. Many executives in that position transition toward investing, advisory roles, or board seats while gradually stepping back from the industries they helped shape.

Instead, Lawson turned toward a problem that operates at a far larger physical scale than software.

He began building a fusion energy company.

His new startup is called Inertia, and it has already raised roughly $450 million from investors including Bessemer Venture Partners and Google’s GV. Its ambition is not incremental improvement to existing energy systems but the commercialization of one of the most difficult technologies humanity has ever attempted to harness: controlled nuclear fusion.

For decades fusion has been described as the ultimate energy source. Scientists have long understood the reaction that powers the sun and every other star in the universe. What has remained elusive is building machines capable of producing that reaction repeatedly, reliably, and at the scale required to generate electricity for cities.

That gap between scientific understanding and industrial reality is where companies like Inertia are now operating.

A Small but Telling Detail

Companies attempting to build infrastructure designed to operate for decades often pay attention to small signals of permanence early on.

Before Inertia publicly launched, the team secured the domain Inertia.com, which had long been owned by domain investor Andrew Rosner. The company worked with Snagged to negotiate the acquisition and bring the domain under its control ahead of launch.

For a company attempting to commercialize fusion energy, the domain itself is a minor detail, yet the name carries a certain resonance. Inertia is a fundamental concept in physics describing the tendency of objects to maintain their state of motion unless acted upon by an external force.

For a company attempting to reshape how energy is produced, the term feels less like branding and more like language drawn directly from the discipline itself.

Why Fusion Matters

Fusion occurs when two light atomic nuclei combine to form a heavier nucleus, releasing energy in the process. During the reaction a small amount of mass disappears and converts directly into energy, (according to Einstein’s equation E = mc²), producing an enormous release of power relative to the amount of fuel consumed.

This is the same process that powers the sun.

Scientists have pursued fusion for decades because of the scale of what it could enable. Fusion reactions produce no carbon emissions and generate far less long-lived radioactive waste than traditional nuclear fission. The fuel used for fusion reactions comes from isotopes of hydrogen, elements that are widely available.

In principle, a functioning fusion power plant could generate vast quantities of electricity while producing minimal environmental impact.

The difficulty lies in creating the conditions required for the reaction to occur.

Atomic nuclei repel one another because they carry positive electrical charges. Overcoming that repulsion requires temperatures and pressures high enough to force the nuclei together. In stars these conditions are maintained by immense gravitational forces. On Earth, scientists must recreate them artificially using sophisticated engineering systems.

Achieving those conditions, even briefly, pushes technology to extremes rarely encountered in industrial machinery.

The Approach Inertia Is Pursuing

Inertia focuses on a method known as inertial confinement fusion, which attempts to create fusion reactions using extremely powerful laser systems.

In this approach, a tiny capsule containing fusion fuel sits inside a chamber surrounded by high-energy lasers. When the lasers fire simultaneously, they deliver an intense burst of energy to the outer surface of the capsule. The outer layer rapidly vaporizes, causing the remaining material to implode inward.

This implosion compresses the fuel to extraordinary density and temperature. For a fraction of a second the conditions inside the capsule resemble those found in the interior of a star. Atomic nuclei collide and fuse together, releasing energy.

For many years the central challenge in fusion research was achieving what scientists call net energy gain, meaning the reaction produces more energy than the system consumes.

In 2022 researchers at the National Ignition Facility in California reached that milestone. Using the world’s most powerful laser system, they triggered a fusion reaction that released more energy than the lasers delivered to the fuel capsule.

The experiment lasted less than a billionth of a second, but its significance was enormous. For the first time, a controlled fusion reaction produced more energy than it consumed.

The physics appeared viable, and what remained was engineering.

The Engineering Mountain

Turning a laboratory experiment into a functioning power plant introduces an entirely different category of complexity.

A fusion experiment fires once, and a fusion power plant must fire repeatedly, potentially several times per second, every hour, every day.

Each reaction requires a precisely manufactured fuel capsule roughly the size of a peppercorn. These capsules must be produced with microscopic precision so that the implosion remains perfectly symmetrical when struck by laser energy.

The laser systems themselves must deliver immense power while maintaining extraordinary accuracy and efficiency. They must fire repeatedly without drifting out of alignment or degrading over time.

After each fusion reaction, the chamber containing the event must absorb the resulting burst of energy. That energy must then be captured and converted into electricity for the power grid while the system prepares for the next reaction moments later.

Every subsystem inside such a reactor represents a formidable engineering challenge. Together, they form a machine unlike anything humanity has previously attempted to build.

Rather than focusing solely on proving that fusion reactions are possible, the company is working on the engineering systems required to make those reactions repeatable, reliable, and economically viable.

A Founder’s Second Act

Lawson’s decision to pursue fusion reflects a shift in ambition that is becoming more common among founders who have already built large technology companies.

Twilio succeeded by abstracting telecommunications infrastructure into software that developers could easily use. Inertia is attempting something analogous at a far larger scale: transforming experimental physics into infrastructure capable of generating electricity.

The difference is that fusion operates on timelines measured in decades rather than short software product cycles. The capital requirements are immense, the engineering problems are unforgiving, and success is far from guaranteed. Yet, the potential impact on the world is immensely large.

A successful fusion industry would provide a new source of energy capable of producing vast quantities of electricity without carbon emissions. The implications would extend across nearly every sector of the global economy.

Even a modest probability of success can justify substantial investment.

The Long Horizon

Fusion research has moved through cycles of optimism and skepticism for decades. Each generation of scientists has believed it might finally possess the tools required to turn the technology into a practical source of energy.

What distinguishes the present moment is the convergence of several developments at once: breakthroughs in experimental physics, advances in engineering capabilities, and the emergence of private capital willing to support long-horizon infrastructure projects.

Companies like Inertia now sit at the intersection of those forces.

The technical hurdles remain substantial, and fusion has historically proven more difficult to commercialize than early projections suggest. Yet, if the effort succeeds, the result would extend far beyond the success of any individual company.

It would mean unlocking a fundamentally new way to produce energy, and that’s the problem Jeff Lawson is working to solve now.

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