mATX Cases (Micro ATX): A mATX Case (or Micro ATX Case) is specifically built to house Micro ATX motherboards. Micro ATX motherboards evolved out of Standard ATX motherboards and oftentimes feature many of the same capabilities and characteristics of the ATX form factor. The main difference between the two is that mATX boards are built physically smaller. The smaller size of mATX Motherboards have made them popular for use in HTPC's and in small form-factor systems. It is important to note that a Full-Sized ATX case will usually be able to support mATX motherboards, whereas a typical mATX case will not be able to house an ATX motherboard.