World’s energy demand has been constantly increasing for decades. Yet, fossil fuels stock, which we use the most extensively, will probably be depleted soon. Moreover, combustion of these conventional fuels leads to excessive carbon dioxide emission. This process causes a multitude of unfavorable consequences for Earth’s climate and biosphere. That is why the scientists have been searching for alternative fuel sources for years. These fuels have to meet some requirements, and general goal is that they must be neutral to the natural environment, truly clean and “green”. One of the possibilities of obtaining friendly energy is biomass processing. Nowadays, a few species of energy plants (e.g. rapeseed, soybean, corn) are used for this purpose. However, traditional cultivation productivity is poor and insufficient and also it occupies the land that would preferably be destined for food and feed production. Algae are potentially a much more efficient source of biomass than all energy plants. They are simple plant-like, photoautotrophic organisms, predominantly single-celled. These so-called microalgae have the ability to grow and divide very fast. In optimal conditions, their cell cycle could last only a few hours. This means that biomass increase is extremely rapid. Cultivation can be supplied with exhaust gases and wastewater, because algae absorbs great amounts of carbon dioxide and nutrients. Some species of microalgae accumulate large amounts of lipids, when treated by nitrogen-starving conditions. Composition of fatty acids is often appropriate for biodiesel production. Biofuels that we can obtain from algal biomass include: bioethanol, methane, hydrogen and more. This review presents fundamentals about morphology, anatomy, physiology and biochemistry of microalgae as well as describes basic information about the cultivation. It characterises some species which could be suitable for energy production, the cultivation devices, methods of cultivation and harvesting and also products that can be obtained from the biomass of microalgae. In the end, there is the balance sheet for the production of microalgae for energy purposes.