Microalgae are mostly photoautotrophic microscopic organisms. According to their cellular structure, they are classified into two types, eukaryotes, and prokaryotes, and they are distributed in all types of ecosystems, presenting unique qualities due to the fact that they synthesize high value-added molecules used in various productive and environmental activities, and because their biomass is used as raw material to obtain various products. Therefore, the objective of this review was to collect, organize, and collate current information on the use of microalgae in the development of biotechnology involving the areas of agriculture, health, food, bioremediation, and biofuels. The results show that the microalga Chlorella stands out for its multiple uses in the five areas considered in this study. The search for healthier and more environmentally friendly technologies has contributed to the development of new biotechnological applications that require the study and incorporation of specialized microorganisms to replace and/or improve existing applications.