In this chapter, we present experimental spectroscopy results necessary to enable precision measurements with YbOH molecules. In particular, we focus on the “science state”—the doubly-degenerate bending mode, denoted \(\tilde {X} { }^2\Sigma ^+(010)\) , and often abbreviated as \(\tilde {X}(010)\) . We present a complete characterization of the science state at high-resolution, including its behavior in electromagnetic fields. Additionally, we characterize the bending mode in the electronic excited state, denoted \(\tilde {A}{ }^2\Pi _{1/2}(010)\) , which we will often abbreviate to \(\tilde {A}(010)\) . We identify a case of a spectroscopic K-resonance in \(\tilde {A}(010)\) state, use the excited state to optically pump into \(\tilde {X}(010)\) , and determine \(\tilde {X}(010) \rightarrow \tilde {A}(010)\) transitions useful for manipulating and probing the science state. The work in this chapter enables us to perform prototype Ramsey interferometry measurements in YbOH in the next chapter, Chap. 5 .