This entry is adapted from https://doi.org/10.3390/jpm12081334. Dendrimers are a special class of synthetic macromolecules, constituted of branches built, step by step, around a central multifunctional core. Each layer of branching points creates a new “generation”. Most of the properties of dendrimers depend on the type of their terminal functions. Dendrimers are often considered as 3-dimensional soft nanoparticles, in opposition to hard metal nanoparticles. Despite the fact that nature has favored branching structures at all levels, from galaxies to trees and to dendritic cells, examples of branching at the molecular level are extremely rare. One can cite glycogen, a branched polymer of glucose, and also some cases of branched lignin, but none of them have a precisely highly branched structure, as do dendrimers. Such unusual structure has generated a many expectations for dendrimers: a huge number of publications and patents exist in relation to medicine, including in relation to personalized medicine but have resulted in very poor clinical translation up to now. This entry focusses on some of the clinical trials carried out with dendrimers.