I'm currently using the MacBook Pro (13'', early 2011) which contains a Thunderbolt port. Unfortunately, the LG UltraFine 5K display uses a Thunderbolt 3 (USB-C) port. That's why I'm currently thinking about connecting them via a Thunderbolt 3 to Thunderbolt 2 adapter.
I'm aware that there were quite a few questions concerning this topic on the Apple homepage. But the answers there weren't really confidable and accurate.