What a half-year for memory.The theme of this group writes itself: nine of the ten are semis/hardware, and the leaders are a memory-and-storage cohort. SanDisk, Micron, Western Digital and Seagate are all riding the NAND/HBM/DRAM shortage colliding with AI data-center demand — SanDisk had already nearly +570% in 2025 as a pure-play flash name leveraged to a global NAND shortage, and the move has only extended. Dell is the AI-server proxy in the group; Corning is the optical/glass infrastructure play. AMD and Applied Materials round it out as the GPU and wafer-fab-equipment exposure.What's equally remarkable is that this isn't about broader chip names. ; NVDA is only +6.28% and AVGO +8.32% YTD, a reminder that index-level leadership and best-stock leadership are very different things this year.If we extend the list to the top-25, it looks like this.The 11–25 band actually broadens the thesis past pure memory into the full AI-infrastructure stack: wafer-fab equipment (LRCX, KLAC, TER), optical/networking (LITE, COHR, CIEN — the transceiver and laser names), and the data-center power-and-cooling trade (VRT, GNRC, FIX, the last being an HVAC/mechanical contractor riding data-center construction). Qnity is the post-spin DuPont electronics-materials business.It's a truly one-theme market when you scale out though. If you had big bets on AI this year, you made incredible gains. If not, it was almost impossible to outperform.The two non-AI standouts are vaccine-maker Moderna at #15 — pipeline/data-driven, a different catalyst entirely — and DaVita at #23, which is dialysis and pure idiosyncratic story. Everything else in the top 25 is some flavor of the same secular bet.Moderna is a platform re-rating away from "COVID one-trick" toward diversified mRNA, which is still a fascinating technology despite the propaganda. The catalysts for the gain was an FDA advisory panel voted 9-0 for its flu vaccine mRNA-1010 in adults 50+, with a final FDA decision due August 5, 2026. Fundamentals are turning too — Q1 2026 revenue was $389M, up 264% YoY and well above consensus. But be careful: the stock trades at ~23x forward earnings on still-uncertain forward numbers. A warning is that insiders have been net sellers, and the sell-side hasn't signed off — the analyst rating skews to Hold/Reduce with price targets implying material downside. The real binary is the Phase 3 melanoma readout later in 2026. This article was written by Adam Button at investinglive.com.