Tomáš Gregor is a materials-science expert specializing in industrial crystal growth, particularly high-purity sapphire and YAG crystals used in optics, electronics, and increasingly biocompatible healthcare materials. He co-founded AT Crystals, a Žilina-based manufacturer in this field, led its rebrand and growth from 2019, and remains a shareholder today. Alongside the business, he is an active researcher, co-authoring peer-reviewed papers with the University of Žilina on improving industrial crystal-growth processes, and has spoken publicly on sapphire-based biocompatible materials for medical use.