The microalgae encompass a varied group of prokaryotes, i.e., cyanobacteria and eukaryotes including protists and unicellular algae. Majority of them are photosynthetic and have been found to play vital roles in managing ecosystems. A good number of these microalgae have been identified so far and subsequently, characterized to reveal their specific roles for a better and more sustainable future of mankind. Recently, they have been employed in agriculture for the supply of food and feed, the making of bioactive molecules along with numerous other significant applications in the pharmaceutical, nutraceutical, cosmetic industries, bioremediation, biofertilizers, carbon sequestration, and biofuel production which have attracted the researchers to study this group of microbes. Their easy cultivation method and minimal requirement of nutrients can be manifested toward their use in the field of bioeconomy. This chapter, therefore, aims to provide an overview of every aspect of freshwater microalgae that is pertinent to biodiversity, bioprospect and bioeconomy for a better tomorrow.