Probiotics are live bacteria or micro-organisms providing health benefits in humans and animals. They are most known for their beneficial support in improving the overall health of the gut. Most of the known used probiotics belong to the lactic acid bacteria. In addition, within the last decade the probiotics have gained attention for their contribution to improved skin health as well. They are currently studied for the fact that their properties apply both to in vivo as in vitro models. Other ways of researching these micro-organisms are with microbiome profiling techniques and genome sequencing, to define in more detail their potential on specific health benefits via microbiome modulations and intracellular mode of action.