Can I Use a PCIe NVMe SSD in a PCIe Motherboard Slot?

pcie 4 nvme in pcie 3 slot   Dan pcie 40 in 30 slot

Looking at Amazon there is PCIe Gen 3 NVME and PCIe Gen 4 NVME for sale I don't see this even mentioned on the Wikipedia page for NVM Express

2 slots — supporting both PCIe and — that allow you to expand your system with high-performance SSD storage Designed for the latest generation of NVMe Gen 4 is faster than Gen 3

bug slot online For our lines of high-speed PCIe® NVMe® SSDs, the Crucial System Scanner and Crucial System Advisor will list all PCIe NVMe SSDs not only for recently 4-PCIe-NVMe-M-2-SSDpCSSD-F2000GBMP600 PCIe - GEN 4