Perfecting of Sa-Ui (寫意, ‘expression of ideals’) is one of the highly pursued artistic achievements in East Asian painting tradition. At the core of those ideals expressed lies the concept of Do (道, ‘the Truth’). As a way of effectively portraying and conveying the ideals of Do, the application of Yeo-Baek (餘白, ‘void space’) is regarded important. This article intends to examine some key issues in understanding the aesthetics of Yeo-Baek. In-depth understanding of Yeo-Baek style makes up a crucial part of the fine art of Dok-Hwa (讀畵, ‘reading a painting’). According to Eastern philosophy, the Truth, or Do, cannot be represented in any language or symbol. This notion is well summarized as ‘the ineffability of Do (道可道非常道)’ in Tao Te Ching (道德經) by Lao Tzu (老子, early 5th century BCE), a leading Chinese thinker. Once you depict something, the depicted image is no longer of the object. In that sense, Yeo-Baek or the void is something ‘depicted without the act of depicting.’ Yeo-Baek is never a fixed, stationary space, but one ‘of dynamic, ever-changing nature, filled with energy’ (氣韻生動). A specific method to present this characteristic of Yeo-Baek is the technique of Hong-Woon-Tak-Wol(烘雲托月), in which, in order to reveal the moon, an artist paints only the surrounding space of the moon, leaving the moon itself untouched. The purpose of such rendering is to achieve ‘the ultimate clear, lucid, and tranquil state’ (空靈). In the East Asian concept of ‘reading a painting’ (讀畵), looking at the painter's brushwork (筆墨) is virtually the same as looking at the empty space or Yeo-Baek of the composition. The brushwork and the empty space are not two separate matters. They are closely interconnected with each other, both philosophically as well as aesthetically. Although often underestimated as mere ‘background’, Yeo-Baek or the void space, which in many cases takes up a large part of the pictorial space, plays a role as significant as that of the brushwork. Thus, the visually empty space in aesthetic sense becomes no longer ‘empty.’The Korean painting tradition has not only exemplified the features of Yeo-Baek, an aesthetic ideal shared in the whole East Asian art tradition, but even went further to intensify and innovate it. In Korean paintings, the effect of Yeo-Baek was made prominent by maximizing the effect of harmonization of a larger space (e.g. one as a main background) and smaller spaces (e.g. ones within objects such as mountains, rocks, tree trunks, and so on). Using a mixture of larger and smaller spaces in a painting composition not only creates the aesthetic effect of providing breezy, fluid, and open feelings to the painting, but also expresses the philosophical notion that each object is not separate from the space or other objects, and that everything, including the space, is all interconnected. It is crucial to note that the Korean painting tradition not merely shares ideals common among the East Asia cultures, such as Sa-Ui and Yeo-Baek, but at the same time, also demonstrates a good number of unique quality and characteristics entirely of its own.