The high millimeter-Wave and Terahertz spectrum above 100 GHz will form the underpinning of a broad set of game-changing future technology including high resolution sensing, imaging, robotics, autonomous systems, and wireless communication. In the last decade, we have seen a tremendous surge in efforts towards enabling chip-scale technology to address signal generation and detection in the THz spectrum. However, there lie several fundamental challenges to translate these efforts into versatile technology that can operate in complex environments that requires properties such as dynamic reconfigurability and rapid adaptability. In this paper, we highlight a new design space that emerges by eliminating the classical block-by-bock design approach. The fundamental principle behind this approach is that the unique wavelength scale at THz (of the order of millimeter/sub-millimeter) is comparable to a typical chip dimension. This wavelength/chip dimension equivalence allows the chip to operate in a new electromagnetic (EM) regime with novel scattering and radiating properties, while the integrated active devices have the ability to actively synthesize, manipulate and sense THz EM fields at sub-wavelength scales. This approach opens up the a new design space that can break many of the trade-offs in the classical design regime. In this paper, we provide design examples that aims towards the ultimate programmable THz sensor/source in silicon-based chips that range from fully integrated chip-scale THz spectroscopes to programmable THz sensors, sources and spatio-temporal modulated arrays for physical layer security. These design examples serve to illustrate the unique opportunities enabled through such a holistic design approach.