This detailed collection provides an accessible compendium of up-to-date methods focused on the study of RNAi and small regulatory miRNAs in stem cells. Beginning with a brief introductory section, the volume continues by exploring methods and protocols for RNAi screening, transfection, and the knockdown of specific genes and pathways in several animal species, including humans and mice, recently developed methods for miRNA expression and functional analysis, as well as usage of CRISPR/Cas 9 to knockout an individual gene for functional studies. Written for the highly successful Methods in Molecular Biology series, chapters include introductions to their respective topics, list of the necessary materials and reagents, step-by-step, readily reproducible laboratory protocols, and tips on troubleshooting and avoiding known pitfalls.