**1. Introduction**

Most multicellular living organisms, especially vertebrates, develop from a single totipotent cell to a multicellular complex adult organism, reflecting an outstanding coordination and organization capacity. Furthermore, in some cases, after organ dissociation, cells can recombine and reconstruct the original structure. Researchers have used that feature to create organ-like structures from stem cells or tissues samples, leading to the formation of structures currently known as organoids [1].

Thus, organoids are self-organizing 3D structures derived from stem cells highly similar in structure and function to actual human organs. The different cell types and interactions guide and make possible this organization process. These structures resemble crucial aspects of the tissues from which derived and thereby organoids allow for biological relevant cell–cell and cell-matrix interactions. Those attributes make organoids technology a valuable tool in multiple applications such as developmental biology, molecular biology, and health studies like pharmacology, disease development and therapy, among others [2, 3].

The organoids field has exponentially accelerated in the last years, mainly after the application of appropriate culturing conditions that allow stem cells to differentiate and participate in cell–cell interactions responsible of the community effect required for optimal resembling of self-organized tissue-like structures.

For instance, the use of Matrigel, a gel protein mixture that mimics the complex extracellular environment found in many tissues [4], has allowed the establishment of the right culture conditions required to achieve 3D cell cultures *in vitro*.

Organoids technology constitutes a step-forward approach for conventional cell-based research, full-filling the gap between 2D cultures and *in vivo* mouse/ human models. Organoids are physiologically more relevant than monolayer culture models, and allow easier manipulation of niche components, signaling pathways and genome editing than *in vivo* models [5].

Therefore, organoids represent a needed and also an advantageous approach in many senses. The organoids technology brings the opportunity to work with 3D-tissue models at a "bench-side" level, opening a wide range of opportunities in basic and clinical research. Moreover, organoids also overcome the problems derived from using animal models to study human physiology and related-diseases. Although many results obtained in animal models can be easily extrapolated, some biological processes are specific to humans [6].
