Microgreens are edible vegetable and herb seedlings with only 1–3 inches. Aside from their remarkable nutritional content, they can be grown easily in the city, and hence, they are acclaimed as emerging functional food. This review aimed to provide a systemic insight into the sustainable agriculture, phytochemicals, and biological activities of microgreens in Southeast Asia. The study was conducted by collecting the experimental findings from scientific articles that were published in reputed journals from the year 2000 to 2021 using electronic databases. The comparative analyses were conducted wherever appropriate. Several species of microgreens from the Brassicaceae, Asteraceae, Lamiaceae, Apiaceae, and Amaranthaceae families were discussed. In the first instance, various methods for cultivating microgreens were explained, followed by the summarisation of phytochemicals (e.g., terpenes, polyphenols, and sulfur-containing compounds) present in microgreens. A comparison of phytochemical composition between microgreens and their mature counterparts (macrogreens) was conducted. Moreover, two well-known biological activities of microgreens, i.e., antioxidant and antimicrobial activities, were outlined, together with their experimental data. Additionally, the effects of human health upon the consumption of microgreens were also elaborated.