Nvidia (NASDAQ: NVDA) stock is falling in Tuesday's trading. The artificial intelligence (AI) leader's share price was down 5.5% as of 2:45 p.m. ET amid a 0.9% decline for the S&P 500 index and a 1.6% pullback for the Nasdaq Composite index.

NVIDIA (NASDAQ: NVDA) is still the most important stock after two-plus years of dominating the stock market. Its GPU technology unlocked the door to AI, and now NVIDIA is capitalizing on it using a full-stack method.

Investors are always scanning the horizon for the next big thing in stocks. For the past few years, it's clear that Nvidia (NASDAQ: NVDA) has been the key winner that's driven most index (and portfolio) returns.