The biological development of a human is an extremely complex and delicate process. It starts from fertilisation and continues until long after birth. The creation and development of the brain is particularly complicated and susceptible to disruptions to its progression. The primary cells responsible for the development of the brain are the neural stem cells. These are a broad class of cells that can differentiate into the wide range of cell types that form the adult brain. To achieve this complex process, different cells need to undergo a range of gene expression changes at the right time. This is delicate and its disturbance is a key cause of pathology in a wide range of diseases. There are many external factors that are known to disrupt neural development however, there are several common chemicals whose effects remain largely unknown. One such group are broadly described as nanoparticles. These are small particles that are being increasingly used by many industries as they can help in the creation of products with better properties. However, their effect on the environment and the human body – particularly that of a developing brain – have been largely unexamined. Associate Professor Ken Tachibana of the Division of Hygienic Chemistry, Sanyo-Onoda City University, Japan is researching the effects of nanoparticles on neural development.