Carbon dots (CDs) have recently triggered great attention in the research of material science and biomedical engineering due to their unique properties. They have been widely explored for applications in printing, photocatalysis, bioimaging, sensing, drug delivery, and nanomedicine. In this presentation, I will firstly introduce preparations of diverse CDs. Particularly, extensive structural characterizations have been performed to build comprehensive structural models for 3 distinct CD species derived from both top-down and bottom-up approaches. Then, I will mainly focus on various applications of the CDs developed in our lab: (1), glucose-based CDs could cross the blood-brain barrier (BBB) due to the presence of glucose transporter proteins on the BBB; (2), carbon nitride dots conjugated with anti-cancer therapeutic drugs and a targeting molecule were capable of effective treatment against diffuse large B-cell lymphoma both in vitro and in vivo; (3), metforminderived CDs showed a unique nucleus targeting property; (4), CDs have constantly shown the capability to inhibit the formation of amyloid precursor protein (APP), beta-amyloid (Aβ) and Aβ fibrils. CDs are promising nanomedicine and drug nanocarriers to treat Alzheimer’s disease; (5), photocatalytic degradation of diverse water pollution models revealed a remarkably enhanced photocatalytic activity of gel-like compared with most known CD species and comparability to graphitic carbon nitride (g-C3N4). In addition, the degradation rate constant was further improved by 1.4 times by embedding g-C3N4 in G-CDs; (6), a pilot study showed a versatile nanocarrier could be assembled via the direct conjugation between distinct CDs to fulfill multitasks.