Microalgae are photosynthetic microorganisms that produce a wide range of biocompounds, such as proteins, omega-3 fatty acids or pigments like astaxanthin; with various applications in the pharmaceutical, cosmetic, bioenergy and food sectors. This chapter provides an overview of the compounds and molecules synthesized by microalgae, ranging from polysaccharides to vitamins, minerals and other secondary metabolites. Additionally, the chapter reviews the key biological aspects that influence the production of such biocompounds, including strain selection, strain improvement and cultivation conditions, as well as the biotechnological factors necessary to optimize the production and processing of these compounds, such as cultivation system, extraction and purification. Lastly, the chapter presents the main applications of commercially relevant microalgae-derived compounds, emphasizing the most notable microalgae-based products currently being developed in the global market.