Illustration depicting a cross-section of an exosome, displaying proteins (blue) and mRNA (messenger ribonucleic acid, red) within it. Exosomes are tiny extracellular vesicles that measure roughly 30-150 nanometres in diameter. These vesicles are enclosed by a lipid bilayer and contain a complex cargo of materials derived from the original cell, such as proteins, lipids, mRNA, and DNA. Exosomes play a role in various physiological functions, including waste management and intercellular communication. They have a broad range of applications, such as serving as biomarkers for diseases and vehicles for drug delivery. For a labelled version of this image see F038/6954.