Exosomes or small extracellular vesicles (sEVs) play a pivotal role in diverse intercellular communications, notably in the selective metastasis of cancer cells. The membranes of sEVs exhibit abundance in raft-associated molecules such as sphingolipids. A recent elucidation revealed that sEV membranes manifested a composition characterized by the coexistence of raft-like and nonraft-like domains as discerned by the assessment of fluorescence anisotropy and lifetimes. Furthermore, it turned out that sEVs retain some asymmetry in the inner and outer leaflets. In light of the unequivocal heterogeneity inherent in sEVs, it is imperative to meticulously scrutinize the behaviors exhibited by each subtype of sEV particles. This review proposes a strategy to identify the subtypes of sEV, encapsulating extant findings and prospects.