Micron stock opened Wednesday's session up about 5%, extending gains from Tuesday.

Micron kicked off another day of strong gains on Wednesday, leading the memory-fueled rally that's helped propel indexes to fresh highs. The S&P 500 and the Nasdaq Composite have hit a string of records, extending gains driven by Micron, Western Digital, Sandisk, and other chipmakers, as investors eye memory chip stocks as key winners in the next leg of the AI race. The S&P 500 capped off its longest weekly winning streak since 2023 last Friday. Here's where major indexes stood around 10 a.m. ET: S&P 500: 7,528.19, up 0.12% Dow Jones Industrial Average: 50,702.50, up 0.48% (+240.82 points) • Nasdaq 100: 26,682.411, up 0.10% Micron stock opened Wednesday's session up about 5%, extending gains from Tuesday when the stock rose more than 19%. The gains have pushed Micron's market capitalization above $1 trillion for the first time this week, with shares nearly tripling in value since the start of 2026. Beyond Micron, other memory chip stocks have also notched big gains. Western Digital, Sandisk, and Seagate rose on Tuesday and Wednesday, though by smaller percentages than Micron. The memory rally wasn't exclusive to the US stock market. Taiwan's Taiex and South Korea's Kospi indexes climbed to fresh record highs fueled by their own chipmaker rallies. SK Hynix, a South Korean chipmaker, surged on Wednesday, gaining more than 9% pushing its market cap into the $1 trillion range. Why memory stocks? Chipmaker stocks leading rallies in the AI era is nothing new. Nvidia dominated Wall Street gains in recent years as companies worked to secure compute power to train AI. In the inference era, memory chips are in high demand, driving memory stocks higher. AI relies on on data which is stored on memory chips. Micron, Sandisk, and other memory chipmakers have seen massive gains as a result. What's next? Memory chips aren't the only bottleneck emerging in the AI era. Optical tech stocks have also been stand out stock market performers in 2026. Lumentum, Ciena, and Corning, all optics plays, are some of the best performers within the S&P 500 in 2026. Optical tech helps address the communication problem between GPUs doing the AI computing the server racks within data centers.

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