research fields, such as medicine, biology, and materials science. [1] These different types of optical components usually utilize the reflection, refraction, and diffraction of light to reshape the wavefronts and control the propagation direction of light in real space. [2] Although great achievements have been made in controlling light in various scopes, it is still challenging to manipulate the light direction at the subwavelength scale with the conventional optical devices. [3] The major constraint of controlling light at nanoscale is the diffraction limit of light, where the smallest resolvable feature is at the wavelength scale. The limited resolution hinders the observation of many intriguing phenomena and features at the subwavelength scale, such as biomolecules, cell components, nanoparticles and nanoscale devices. [4-7] New techniques are therefore highly demanded for subwavelength light manipulation. Nanoparticles have been introduced as a bridge to connect the gap between the macroscopic and the microscopic scale owing to their extraordinary optical properties in the manipulation of light. [8,9] In order to design nanoantennas with nanoparticles, many ideas have been borrowed from conventional macroscopic schemes. One of the most famous examples is Yagi-Uda antennas. This antenna structure was first invented by Hidetsugu Yagi and Shintaro Uda in 1926. [10] The traditional Yagi-Uda antennas are usually composed of multiple parallel elements in a line, usually halfwave dipoles made of metal rods, which function as a reflector, a driving element (feed), and several directors. Each director reradiates the electromagnetic waves from the driving element at a different phase, and the reradiated waves from the multiple directors superpose and interfere to enhance the radiation in a single direction. The Yagi-Uda antennas have been widely used in analog television, shortwave communication links, radar antennas, and broadcasting stations. Inspired by this idea, Yagi-Uda nanoantennas consisting of a reflector, a feed, and several directors have also been invented. As the nanoscale counterpart, Yagi-Uda nanoantennas can redirect light emission in a desired direction with a narrow angle and enhanced signal intensity in a nanoscale region. [11,12] The detailed analysis of different Yagi-Uda nanoantennas will be introduced in Sections 3-5. The inspiring work has opened a new era for directional light control at the subwavelength scale. After the development for a decade, the techniques for directional light scattering and emitting have been enriched. Many different Light manipulation has been widely employed in lighting, display, and energy storage, becoming an inseparable part of human lives. However, the conventional optical devices suffer from the diffraction limit of electromagnetic waves. To overcome the limitation, plasmonic and dielectric nanoantennas are introduced for the control of light direction at nanoscale. The directionality of the nanoantennas stems from their electromagnetic resonance properties or ...