Artificial intelligence (AI) stocks are zooming. Even the private market is going like gangbusters. Right now, more than one-fifth of all venture capital funding is going toward AI start-ups, According to a report from Crunchbase.

Want to get involved? Here are two AI stocks that have minted a sizable number of new millionaires in recent months.

1. Nvidia: This 1 stock is the king of AI

No list of red-hot AI stocks would be complete without Nvidia (NASDAQ: NVDA). Global spending on AI systems and services reached $150 billion in 2023. This year some estimates say spending will surpass $200 billion. And that's just the tip of the iceberg. By 2033, Bloomberg Intelligence believes that generative AI will become a $1.3 trillion industry.

These AI applications will be powered by semiconductors, and the world will need a lot of them to meet burgeoning demand. This is why Nvidia's market cap ballooned from $200 billion to nearly $2.4 trillion in recent years. The company simply has a meaningful head start versus its competitors in supplying this rapid-growth industry with the materials it needs to function.

OpenAI's ChatGPT was trained using Nvidia A100 processors in 2022, and its next-gen H100 processors have been manufactured at full capacity for more than a year. According to Fool contributor Harsh Chauhan, "This lead has allowed Nvidia to exercise a solid grip over the AI chip market and also explains why its competitors' latest offerings aren't gaining much traction. For instance, [Advanced Micro Devices] sees its AI GPU sales hitting at least $4 billion in 2024. Intel is further behind and expects the Gaudi 3 launch to help it generate $500 million in AI chip sales in the second half of 2024."

Many investors have already made millions with Nvidia stock, but be aware that most of the company's expected growth is still ahead of it. While sales have picked up dramatically in recent years, Nvidia's market cap growth has far outstripped this sales growth. And the stock's price-to-sales ratio soared -- roughly tripling over the last 12 months. Most of the quick money may have already been made with Nvidia stock, but this is still one of the best investments to make for long-term AI bulls.

2. Looking for the next big AI hit? SoundHound AI stock could be it.

Looking for more rapid growth than a $2 trillion business can likely provide? Take a closer look at SoundHound AI (NASDAQ: SOUN).

Founded in 2005, SoundHound is a voice AI and speech recognition company. Think of its products as the voice-enabled version of automated chatbots. With SoundHound, businesses can give customers a "live" representative capable of giving them customized directions and feedback. For now, its software is particularly well-suited for use cases with a narrow set of typical questions. Restaurants, for example -- one of SoundHound's biggest end markets -- can have a SoundHound AI agent respond to customer queries like, "Do you take reservations?" or "What time do you open?" SoundHound's software could foreseeably have huge adoption in fast food drive-thrus.

Like most AI companies, SoundHound's revenue is small but growing quickly. Last quarter, sales jumped by 73% year over year to $11.6 million. With a $1.75 billion market cap, shares are expensive versus its current sales figures. But long-term growth could eventually make today's price tag look like a bargain. The company has the technology and early market adoption to make that future a reality. As Fool contributor Geoffrey Seiler writes, "If its technology becomes a must-have feature and is widely adopted across devices and industries, then the sky is the limit and today's high valuation will look cheap down the line."

Even Nvidia is bullish on SoundHound stock. Last quarter, Nvidia invested directly in several AI start-ups. SoundHound was one of them, with Nvidia investing $3.7 million for a 0.6% stake. If you're looking for high-upside AI stocks, SoundHound should be at the top of your watchlist.

Should you invest $1,000 in Nvidia right now?

Before you buy stock in Nvidia, consider this:

The Motley Fool Stock Advisor analyst team just identified what they believe are the 10 best stocks for investors to buy now… and Nvidia wasn’t one of them. The 10 stocks that made the cut could produce monster returns in the coming years.

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Ryan Vanzo has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends Advanced Micro Devices and Nvidia. The Motley Fool recommends Intel and recommends the following options: long January 2025 $45 calls on Intel and short May 2024 $47 calls on Intel. The Motley Fool has a disclosure policy.

2 Millionaire-Maker AI Stocks was originally published by The Motley Fool