The background to his paper is the rapid spread of the Zika virus (ZIKV) and its devastating effects in the developing fetus (which has resulted in a global health emergency).  The emergence of human brain organoids represents a novel method to investigate early brain development coinciding with the critical period for ZIKV-infection vulnerability of the fetus. 

His hypothesis is that ZIKV (Zika virus) causes congenital microcephaly, as investigated using human brain organoid models.