Small non-coding RNAs (sncRNAs) are small regulatory molecules, which play key roles in fine-tune of all cell functions. In late 1970s and early 1980s, it was first determined that non-coding RNAs contribute to the cellular regulatory processes. The kingdom of sncRNAs is very numerous and it is clear that functions of different members of this family is different from each other and may be involved in normal and pathologic processes in cell. Recently it was investigated that sncRNAs and long non-coding RNAs play roles in cellular differentiation, proliferation, metabolic processes, bioenergetic regulation, cell death and inter-cellular communications, etc. In embryos, non-coding RNAs control maternal-zygotic transition, the maintenance of pluripotency, the pattering of the body axes, the specification and differentiation of cell types and morphogenesis of organs. Development of hematologic malignancies in humans, their course and regulation of resistance and sensitivity of tumorous cells to therapy are under the control of sncRNAs.