Activation tagging is a powerful strategy to find new gene functions, especially from genes that are redundant or show lethal knock-out phenotypes. It has been applied using T-DNA or transposons. En/Spm-I/dSpm engineered transposons are efficient Activation tags in Arabidopsis. An immobilized transposase source and an enhancer-bearing non-autonomous element are used in combination with positive and negative selectable markers to generate a population of single or low copy, stable insertions. This method describes the steps required to select the best parental lines, generate a population of stable insertions, and gene identification.