The Micro ATX is basically a form-factor and power supply design of motherboards. It is also referred to as uATX, μATX, and mATX. This standard form factor of the motherboard was first revealed to the world in the December of the year 1997.
The size dimensions that you get in this form factor of the motherboard will be 9.6 inches by 9.6 in 244 x 244mm. If you consider and compare it with the standard full-sized ATX Motherboard it is exactly 1-fourth times longer with dimensions; 12 by 9.6 in 305 by 244mm.
The microATX motherboards were clearly designed with the intention of giving a product that is backwardly compatible with the full-sized ATX. The clutching mounts of these micro-ATX motherboards are the exact same as the ones that are used in the ATX form-factor motherboards, looking closer you will notice that even the IO shield is exactly matching.
Due to the fact that these two have the same mounts and other units, thus the microATX motherboards can be considered for usage in a full-sized ATX. Many of the microATX motherboards are mostly seen using the exact power figures as the ATX form factor of motherboards, which thereby permits the usage and combination of ATX motherboards with the microATX motherboards.
The expansion slots and units like southbridge extensions and northbridge ports used in the ATX motherboards are given instantly the same in the microATX motherboards that directly enable them to consume and take almost every component of the ATX MOBOs. Nonetheless, you can make a final mental understanding that all the micro ATX form factors of motherboards are equally advanced and usable as the ATX motherboards. Since they are smaller in size by inches or two from the ATX mobo, they lack the number of ports and expansion slots that you can see in the ATX MOBOs.