Neurulation, illustration. This process is the transformation of the neural plate into the neural tube. The sequence runs from upper left to upper right to lower left to lower right. The embryo is termed a neurula during this process. A developing baby is an embryo from just after conception to around 8 weeks. It is then known as a foetus. The brain and nervous system develops following neurulation, with primary structures present by week six, and cortical folds appearing between weeks 24 and 32.