Zero trust (ZT) is a new concept involving the provisioning of enterprise/organization resources to the subjects without relying on any implicit trust. Unlike the perimeter-based architecture in which any subject behind the wall (i.e., inside the predefined perimeter) is considered trusted, zero trust architecture (ZTA) processes any request and provides a resource to the subject without relying on implicit trust. In this paper, based on NIST Special Publication SP800-207, the concept of ZT and ZTA is introduced. Also, challenges, steps, and things to consider when migrating from the legacy architecture to ZTA are presented and discussed.