TechRadar outlines the differences between different motherboard sizes and their different features and functionality ...

The typical size of an ATX motherboard is about 9.6" x 12". EATX: 13" x 12" -- A fully-featured ATX motherboard with an extended width of 13" and height of 12" instead of ATX's maximum of 12" x 9. ...

including the typical around-10.6-inch-deep enthusiast models that sometimes get tagged with today's semi-imprecise Extended ATX (EATX) label. The range of boards that the 600 will fit thus includes ...

As can be evidenced from the motherboard size chart above, there's quite a dramatic difference in scale between Mini-ITX and MicroATX, with more of a subtle difference when comparing ATX and EATX ...