Neuralink

Sierra

Neuralink

Neuralink doesn't have a traditional revenue model yet — it's still in clinical trials. The near-term plan is medical devices sold to hospitals and clinics for treating neurological conditions.

Brain-computer interfaces for paralysis, ALS, blindness, and other conditions would be reimbursed by insurance and healthcare systems, similar to cochlear implants or deep brain stimulators.

The long-term vision is consumer neurotechnology — healthy people choosing to get brain implants for enhanced cognition, communication, or AI interaction. This is years or decades away and faces massive regulatory and ethical hurdles.

But if it works, the total addressable market is literally every human brain on the planet.

The surgical robot is potentially a separate revenue stream. Even if the implant itself doesn't dominate, the precision robotics technology developed for neural surgery could be licensed to other medical device companies.

Neuralink has also built custom chip fabrication capabilities that could have applications beyond brain interfaces.

Sierra

Companies pay Sierra to run their customer service with AI agents instead of hiring rooms full of humans. The agent talks to your customers over chat.

It answers questions. It processes returns.

It updates subscriptions. Here is the clever part.

Sierra charges based on outcomes, not seats. Brands pay when the AI actually resolves a problem, not just for having the software installed.

That pricing is unusual. Most software charges a flat monthly fee no matter what.

Sierra only gets paid when the bot does the job.

Neuralink

Elon Musk had been talking about brain-computer interfaces publicly since at least 2016. His stated motivation was existential: if AI becomes superintelligent, humans need a way to merge with it or risk becoming irrelevant.

The solution, in his mind, was a direct neural link between the human brain and computers.

Neuralink was quietly incorporated in July 2016 in California. Musk recruited a team of eight co-founders — neuroscientists, engineers, and chip designers from institutions like UC Berkeley, MIT, and Lawrence Livermore National Laboratory.

The founding team included Ben Rapoport, a neurosurgeon who understood both the medical and engineering sides, and Dongjin Seo, who had done PhD research on neural dust (tiny wireless brain sensors).

The company operated in stealth for two years before a 2019 presentation where Musk revealed the vision: a coin-sized device implanted in the skull containing thousands of ultra-thin electrode threads inserted into the brain by a custom-built surgical robot. The threads are thinner than a human hair — roughly 5 microns wide — and each one contains multiple electrodes that read neural signals.

The robot was necessary because no human surgeon could place threads that thin without damaging brain tissue.

Sierra

Bret Taylor had already done the impossible twice. He co-created Google Maps.

He later became co-CEO of Salesforce, chaired Twitter's board during the messy Elon Musk takeover, and became chairman of OpenAI in late 2023. Clay Bavor spent 18 years at Google, most recently running its Labs group.

The two friends left their big jobs in 2023 to build something together. They picked customer service on purpose.

It is the least glamorous corner of software. Their logic was simple.

Companies hate their support costs. Customers hate waiting on hold.

AI that actually resolves problems could fix both sides at once. They launched Sierra in February 2024 with $110 million from Sequoia and Benchmark.

Neuralink

Neuralink's growth strategy is the classic Musk playbook: start with the premium use case that justifies the cost, then scale down. Phase 1 is medical — treat severe neurological conditions where no other option exists.

Quadriplegia, ALS, locked-in syndrome. Patients who literally cannot move or speak are willing to undergo experimental brain surgery.

The FDA granted Breakthrough Device designation in 2020, and the first human trial (PRIME study) began in 2024.

Phase 2 is expanding medical indications — blindness, depression, epilepsy, Parkinson's. Each new condition multiplies the patient population and the regulatory pathway, building clinical evidence along the way.

Phase 3 — the moonshot — is consumer enhancement. Musk has described this as "conceptual telepathy," where you think a message and it sends.

This phase requires proving extraordinary safety over years of medical use first. Nobody is going to electively implant a brain chip unless the medical version has been proven safe for a decade.

Sierra

Sierra went straight for big brands, not tiny startups. SoFi, Ramp, ADT, Sonos and Brex signed up early.

By 2026 it said more than 40% of the Fortune 50 were customers. The trick was trust.

Enterprises are terrified of an AI bot going rogue and insulting a customer. So Sierra built guardrails and let each company control exactly how the agent behaves.

Bret Taylor's contacts did the rest. When the chairman of OpenAI calls a Fortune 500 CEO, they pick up.

Sierra hit $100 million in annual recurring revenue in November 2025, seven quarters after launch, and $150 million by February 2026. In April 2026 it launched Ghostwriter, which builds and deploys a new agent from a plain-English description.

Neuralink

The FDA and regulatory approval process is the primary bottleneck. Brain implants are Class III medical devices — the highest risk category.

Every design change, every new indication, requires extensive clinical data. The USDA also investigated Neuralink in 2022 for potential animal welfare violations in their primate testing program, which created PR headaches.

Long-term biocompatibility is an unsolved problem. The brain treats any foreign object as an invader and forms scar tissue around it, which can degrade signal quality over time.

Making an implant that works reliably for decades inside a hostile biological environment is one of the hardest engineering problems in medicine. Neuralink's thread retraction issue in their first human patient — where some threads pulled away from the brain — highlighted how much work remains.

Talent retention has been rocky. Max Hodak, the original president, left in 2021.

Several founding scientists departed. Working for Musk is notoriously demanding, and the timeline pressure on a medical device company clashes with the inherent need for cautious, methodical development.

Sierra

Everyone is building AI customer service agents right now. Decagon has raised at a multi-billion valuation.

Salesforce, ServiceNow and Intercom all shipped their own agents. Sierra is not the cheap option.

It sells premium AI to giant companies that move slowly. The bigger risk sits underneath the product.

Sierra does not make its own AI models. It rents them from providers like OpenAI and Anthropic.

If those model makers decide to compete directly, Sierra's edge gets thin fast, and its co-founder chairing one of them only makes that question louder. A $15.8 billion valuation on roughly $150 million in revenue leaves almost no room for a stumble.

Neuralink

The N1 Implant — a coin-sized device (23mm diameter, 8mm thick) implanted flush with the skull containing a custom chip that wirelessly transmits neural data to external devices via Bluetooth. The R1 Robot — a precision surgical system that inserts 64 flexible threads carrying 1,024 electrodes into the brain with micron-level accuracy, avoiding blood vessels using computer vision.

The N1 User App — software that translates neural signals into computer commands, allowing users to control cursors, keyboards, and eventually robotic limbs through thought alone. BCI Software Platform — the signal processing and machine learning stack that decodes raw brain signals into intended actions.

Sierra

The core product is the Sierra AI agent. It is a branded customer service bot that companies deploy on their website, app, and phone lines.

It handles the boring stuff. Order tracking.

Refunds. Password resets.

Account changes. Sierra also built its own tools to test and monitor these agents so they do not make things up.

In 2024 the company added a voice version that talks to customers on the phone. In April 2026 it added Ghostwriter, a tool that builds and deploys a new agent from a plain-English description.

The whole pitch is one AI agent that carries your brand's name and never sleeps.

Neuralink

Elon Musk has been the primary funder, investing hundreds of millions of his personal wealth. The company raised $205 million in a Series C in 2021, then $280 million in a Series D in 2023 led by Founders Fund (Peter Thiel's firm).

A 2024 round reportedly valued the company at $8.9 billion. Google Ventures (GV) and DFJ Growth have also participated.

The investor base is narrow compared to most startups at this valuation.

Sierra

Sequoia Capital and Benchmark wrote the first checks at launch in February 2024, $110 million between them. Greenoaks Capital then led both the $175 million round in 2024 and the $350 million round in September 2025.

In May 2026 Tiger Global and Google's GV led a $950 million round at a $15.8 billion valuation, with Benchmark, Sequoia and Greenoaks back in. That takes total funding to about $1.6 billion.

That is partly the product and partly Bret Taylor. Investors bet on founders who have already built billion-dollar things.