**1. Introduction**

Extracellular vesicles (EVs) are nanoscale vesicles secreted by cells that mediate horizontal cargo transport from donor to recipient cell, thereby establishing

#### **Figure 1.**

*Centre: showing exosome composition, including proteins, lipids, carbohydrates, nucleic acids, mRNA, miRNA, non-coding RNA, and DNA. Proteins in the exosome include heat shock proteins (HSP), cytoskeletal proteins (ESCRT components), membrane transporters, fusion proteins, growth factors and cytokines, Tetraspanins, Flotillin, ligands like TRAIL (TNF-related apoptosis-inducing ligand), FasL (Fas ligand) and receptors like TfR (transferrin receptor). The different methods commonly used for exosome isolation is shown in the yellow ring. Four corners: shows the different sources of exosomes, including bodily fluid, somatic cells, stem cells and diseased.*

#### **Figure 2.**

*Exosome biogenesis: exosome biogenesis initiates with the intraluminal vesicles (ILVs) formation within the multi-vesicular body (MVB), followed by the fusion of MVB with the plasma membrane. After fusion, these ILVs are secreted as exosomes, although some are chosen for destruction by the lysosome. Exosomes carry lipids, RNA, DNA, proteins, adhesion molecules, receptors, and other functional.*

cell-cell communication and signaling [1]. EVs are lipid bilayer-delimited particles released spontaneously by almost all types of cells. The EVs contain cargo, including proteins, nucleic acids, lipids, metabolites, and even organelles, representing the parent cell's physiological state (**Figure 1**) [1, 2]. There are three primary subtypes of EVs identified by their size and biological processes; exosomes (~30–150 nm), microvesicles (~100–1000 nm), and apoptotic bodies (~1000–5000 nm). The exosome biogenesis process is quite intriguing where multivesicular bodies (MVBs) are specialized endosomal compartments containing multiple intraluminal vesicles (ILVs). ILVs are generated by the inward budding of endosomal membranes within MVBs and followed by MVBs fusion with the plasma membrane and extracellular exocytosisbased release as exosomes (**Figure 2**) [3]. Microvesicles are generated by the budding outward of the healthy cell's plasma membrane. In comparison, apoptotic bodies are plasma membrane blebs of cells that originate during apoptosis. Several EV subgroups have been hypothesized, including ectosomes, microparticles, oncosomes, and others, in addition to the three primary forms, but the dearth of established biomarkers and the lack of standardized isolation techniques have resulted in misconceptions in classifying EV subgroups [4]. This book presents a comprehensive overview of EVs and has three sections: the biology of extracellular vesicles; the second is the role of extracellular vesicles in human diseases, and third is extracellular vesicles and cancer.
