This protocol describes transfection of ribonucleoprotein (RNP) complexes that consist of purified Cas9 nuclease duplexed with synthetic guide RNA in cultured cells using the AMAXA Nucleo AMAXA Nucleofector II Electroporation system using Program X-001.RNPs complex have only transient expression inside the cell, this allows for the highest levels of editing efficiency and greatly reduces the chances of possible off target and toxic effects of integration of foreignDNA in host genome