Intel has released a new official motherboard form factor. Smaller than ITX yet bigger than their NUC's called 5x5. 29% smaller than ITX comes in at 147x140mm (5.5x5.8 inches) which makes it the smallest form factor with a socket on the market. Supports the LGA socket, from Celeron to Core I7 with a max TDP of 65watts, more specs are listed below. The one thing gamers need to pay attention to is that it DOES NOT support PCI. Only iGPU's can be used. This is one reason many people believe it will be more for OEMs than consumers for future SFF builds.
Source:
PC Gamer