The applications of cell cultures and transgenic plants in several aspects of modern biotechnology are reviewed. The usefulness of cell cultures in biosynthetic pathway investigation, micropropagation, development of new varieties, genetic mapping and gene functioning analysis and industrial production of bioactive compounds are pointed out. The emphasis of this review is also laid on scientific aspects of transgenic plants. They are successfully used for promoters and other gene regulatory sequences study, investigation of plant primary and secondary metabolite pathways and for improving both the productivity and quality of crops. Since there is a risk to transgenic plant technology mainly because of antibiotic resistance used for transgenes selection, several methods have been worked out for release marker gene which are also briefly reviewed.