This presentation will describe  the subsystems of the Thirty Meter Telescope Observatory (TMT), with a focus on the technical aspects. In general, large observatories  have similarities and differences that depend on their Science Requirements and architecture choices. Unique technical solutions are selected for the subsystems of each observatory to create one-of-a-kind complex assemblies to support the desire astronomical outcome. The subsystems that will be covered will include:  Enclosure, Telescope, Adaptive Optics System and First Light Instruments. Some of the technical choices that influence the final astronomical capabilities of the TMT will be also presented.