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Figure 2. The progress of 143 clinical trials involving EVs worldwide [www.clinicaltrials.gov (Accessed: August 2021)]. (A) The number of studies on EVs by physiological structure. There are 22 categories according to the body structure in 143 studies. (B) The number of studies on EVs is classified according to country and project progress status. According to country classification, 27 countries participated in the 143 studies on exosomes, and there are nine research statuses in 143 studies. (C) The percentage is presented based on the research purpose. There are four different directions of EV-based research, including diagnosis, treatment, monitoring, and mechanism. (D) The contents of EVs were evaluated in 108 studies. Others were used to illustrate an unclear description. (E) The proportion of cell sources used for the treatment with EVs in 42 studies. There are nine therapeutic sources of EVs, mainly originating from MSCs. (F) According to the definition presented by the US Food and Drug Administration (FDA), the number of studies in each clinical trial stage is shown. “Not Applicable” is used to describe trials without FDA-defined phases. EVs: Extracellular vesicles; MSCs: mesenchymal stem cells.