Abstract
How does a fertilized egg give rise to the more than 200 types of differentiated cells in our bodies? As Verrijzer explains in his Perspective, different components of the general transcription factor TFIID, such as the TAFs, ensure that crucial developmental genes are switched on in a tissue-specific manner. Thus, TFIID, which has always been considered a general transcription factor, can be tailored by TAFs to the specialist needs of developing tissues.