This chapter introduces the experimental study of fundamental symmetry violation, specifically parity (P) and time-reversal (T) violation, using cold molecules. We motivate the search for new, symmetry violating physics beyond the Standard Model (BSM) to generate the imbalance of matter and antimatter in the universe, which cannot be explained by the Standard Model alone. We overview the use of heavy atoms and molecules to probe fundamental symmetry violation, and explain the connection between precision measurement constraints and theories of high energy physics. Finally, in this chapter we motivate the use of polyatomic molecules, such as YbOH, as a promising platform for next-generation measurements. We introduce key aspects like laser-cooling, quantum control, and the advantageous structural features of polyatomic molecules.