This is done before construction begins, but can be dangerous if not done properly. Choosing PC parts is fun on paper, but a little oversight can lead to incompatibilities – and even if the parts work, they won’t work together.
The most common examples of this are motherboards, processors, and coolers, but these three components can cause other incompatibilities, such as an SSD or graphics card. That’s why, when compiling your parts list, it’s a good idea to use a tool like PCPartPicker to check if they match. Better yet, read the description of each section and see if it adds up.
Remember that each motherboard only supports one type of CPU socket. In AMD’s case, that would be AM5 for the AMD Ryzen 7000; for Intel, we are talking about LGA1700, and the socket supports Alder Lake (12th-Gen) and Raptor Lake (13th-Gen, as well as 14th-Gen Raptor Lake refresh processors). Trying to use one of the motherboards with a different CPU will not work, and vice versa.
Older motherboards are not compatible with M2 SSDs, which means you can have an SSD without anywhere else. They can also have enough PCIe lanes or slots for other large graphics cards. Small PC cases do not support a large motherboard, but also large graphics cards like Nvidia’s RTX 4090.
For a quick recap, the easiest way to assemble your hardware is to choose a CPU and GPU and go from there. Check that it fits the socket and the amount of slope for each method, and consult a professional if you are not sure.