To answer the question, at a minimum the volumes that have a status of "boot" and "system".
This has nothing to do with the question, but I've done this migration a few times on laptops with one bay drive and it can be a painful and a very time-consuming process, especially if your source partition is larger than the target volume, which is somewhat common due to the expense of SSDs, and you have to move data around in huge GB chunks and then shrink the "boot" volume to fit on the target.
What I found that seems to be the least painful path after shrinking the source volume is to place the SSD in a USB caddy, download clonezilla.org and use a USB drive to boot up clonezilla to clone the source partitions perfectly to the source SSD in the USB caddy. Then I simply placed the SSD back in the laptop and it just worked.
Now, of course, installing the OS on a fresh drive is the cleanest option, but reinstalling and configuring everything and ensuring you have all install files, drivers, license keys or credentials, etc. can take weeks to complete depending on the scenario. "Been there, done that". Cloning is an awesome option for migrating if you don't have the time to reinstall from scratch.
Edit/Update: I don't have enough reputation points to reply to the below "warning" about cloning. As I've stated, I've cloned numerous times even since posting the original message due to drive failures. The OS works fine in EVERY instance after using clonezilla. I'm not trying to sell it (it's free)...just stating a fact. The system is no slower than before. Even after a clean OS install, all Windows systems will degrade in performance as more changes and applications are installed. Your opinion is yours. My real world experience is mine. Best of luck.