In glioblastoma, tumour heterogeneity is thought to underlie the poor efficacy of treatments. Now, using a novel surgical multisampling scheme, Sottoriva et al. have revealed the true extent of intratumoural heterogeneity. Numerous subtypes of glioblastoma were uncovered in each of the 11 individuals studied, and various regions of the tumour were at different stages of progression. The findings suggest that novel treatment strategies for glioblastoma are needed.