Small form-factor PCs are back in Vogue. Specifically, mini-ITX, which was first developed by VIA in the late 2001, but has really taken off in popularity in the last couple of years. While motherboards remain the backbone of a PC, and thus its principle size direction, a supporting eco-system of smaller size components needs to accompany it for everything to fit. Where high-performance CPUs have dropped in power consumption; from 100+W to 95W, then 77/65W or even lower, graphics cards mostly have shown the opposite trend, with the fastest parts hitting near 300W. They accommodate physically larger cores, additional memory, power circuitry and enlarged coolers, to the point that they often dwarf mini-ITX motherboards, making it difficult to find cases to accommodate them.
ASUS GTX 670 DirectCU Mini: Small Size, Full Power - Republic of Gamers