exemplified using the high value green alga H. pluvialis. In order to profit from possible benefits of transgenic microalgae, outdoor cultivation in open ponds must be applied. Most recent advances in genetic engineering of microalgae are based on the use of bacterial antibiotic markers that can represent significant regulatory obstacles for cultivation and marketing of the resulting algal biomass. Microalgae are not included in most current regulatory EU documents concerning genetic engineering. For most matters of biological safety microalgae can be considered microorganisms, such that transgenic microalgae would fall under regulations in the “Guidance Document of the EFSA genetically modified organism (GMO) Panel on the risk assessment of genetically modified microorganisms and their derived products intended for food and feed use” (http://www.efsa.europa.eu/en/efsajournal/pub/374.htm)