brain tissues (Eiraku et al., 2008) and optic cups (Eiraku et al., 2011; Nakano et al., 2012). Induced pluripotent stem cells, a breakthrough that took place in 2007, have provided an additional tool to study morphogenesis (Takahashi et al., 2007; Yu et al., 2007; Park et al., 2008). Lancaster et al. (2013) established a culture method that allowed the generation of cerebral organoids from induced pluripotent stem cells derived from skin fibroblasts from a patient with microcephaly. In a recent review, Kelava and Lancaster (2016) outlined the importance of the ECM and the microenvironment in the recent advances in organoid cultures of brain tissues, implicitly demonstrating the relevance the last century has had in the current advances. In the context of the methodological and experimental journey we have revisited in this article, we define an organoid as a unit of function of a given organ that is able to reproduce, in culture, a biological structure similar in architecture and function to its counterpart in vivo. The origin of this unit is today multiple, as it can come from a fragment of tissue, a stem cell located in an adult organ, an embryonic stem cell, or an induced pluripotent stem cell.
