The small noncoding RNAs, unlike the canonical regulatory protein factors, regulate messenger RNA stability, protein synthesis, chromatin organization and genome structure by RNA interference. Owing to its apparent overarching control and ease of manipulation, RNAi has been extensively used as a tool for investigating gene function and is being exploited as a potential therapeutic tool through silencing. Small RNAs effect gene silencing through RNAi machinery —— the effector complexes of RNAi, which contain multiple protein components. Here, a few impressive progresses in understanding the role of the key proteins in RNAi machinery through studies of their structure and function were reviewed.