In this one-day workshop, the participants learn to handle the essential tools and protocols required for planning and execution of a CRISPR/Cas9 mediated gene-editing project. In the morning, the outline of exemplary knockout and knockin allele designs will be demonstrated on screen and will be recapitulated by the trainees in real time. The ApE plasmid editor will be used as a free DNA sequence handling software; however, personal laptops and preferred software can be brought as well. In the afternoon, the tutors will coach the planning and troubleshooting of individual projects provided by the trainees. Finally, selected projects will be presented to the entire class and discussed. Trainees are encouraged to submit their favored gene editing project(s) (gene, intended mutant allele, cell type and organism) in advance to the organizers to enable optimal preparation. The course will be of use for scientists and technicians at any level, which plan or already started to use CRISPR gene editing for their research. Although the focus will be on mammalian cells, however, also projects on plant and bacteria cell lines may be submitted. Trainees will be provided with an essential set of tools and protocols, enabling them to proceed independently.