If we define theatre as an infinite tower piled up by smoke, the strata of the organic composition of an actor's/actress' body-mind-spirit, may not only be complicatedly worked out, but it seems to belong to a non-scientific realm. However and at the same time, it is also true that the audience is eager to witness a certain kind of specific vitality from the actor/actress on stage. Of course the vitality is hard to be prescribed. Simply we call it a texture of energy, nuance of existence, or much simpler, an actor's/actress' 'aura'. That is, the existential nuance of the actor/actress. The nuance, which is surging from the actor's/actress' authentic presence, ultimately comes out of, not the circumstantial interpretation of the production but the power of its integration. We can find from the works of Meyerhold, Grotowsky and Barba the theatrical fact that the actor's aura can be obtained by a kind of artificiality rather than innate characteristics of existence. These directors commonly regard theatre as the actor's/actress' theatre. Respectively choosing his own specific methods of expression, they unexpectedly meet in a same spot in which actor's/actress' theatre can be realized by the rediscovery of the actor's/actress's body-form. In other words, their approaching methods to theatre look alike, at least in that abandoning reserving any natural, unconscious, economic body-form of an actor/actress, they rather try to discover a certain kind of 'technical' body-form. The form which is totally non/un-conscious, unfamiliar and non-economical. Their research process explores an ideal body-form, and this thesis focuses on this point. For this work, I bring the notion of 'liminality' that connotes the praxis for essential presence of the actor/actress as well as the incubating time and space nacessary for his/her rebirth. And for developing this work, I ask: Could not the actor's/actress' consciousness and the spatiotemporal dimensions (s)he meets, be possibly defined as the core of liminality, only in case that (s)he requires them in the process of, either exploring the unfamiliar body or familiarising with the unfamiliar body-form? As I mentioned above, the three frontiers' theatrical journey is similar in part. For example, three all start from the actor's/actress' consciousness and then go through the body enlarged with it. Then they continue their journey, but different from one another. Meyerhold still uses the conscious body. But now he transforms it into a kind of mobilized sculptures. In comparison with Meyerhold's use of the consciousness, Grotowsky puts his emphasis on an autonomous body which, if necessary, cast away even the innate consciousness. Likewise, to Barba, theatre always starts from the actor/actress who has already taken off all kinds of conventions. (Conventions should be re-designed!) The actor/actress therefore recreates him/herself as his/her body-mind wears a new, unfamiliar, readjusted form and vitality. And then this restructured body-mind may unceasingly aim at exploring its vitalized 'positive organism', that is the waves of self-centering energy, an existential nuance, and an authentic (or maybe behavioral) expressiveness. Now it seems clear that the liminal process for the frontiers' theatrical journey could be equalized as a profound process of self-penetration, self-transformation, and self-realization. This thesis explores the mystic realm of liminality.