Bob Löwenberg, MD, PhD, from Erasmus University, Rotterdam, Netherlands, summarizes new data on molecular heterogeneity of acute myeloid leukemia (AML) at the International Symposium on Acute Leukemias (ISAL) 2017 in Munich, Germany. He discusses how AML is a very complex disease, both in the genetic abnormalities it acquires and its sub-clonal structure. Prof. Löwenberg describes a session at ISAL 2017 which covered molecular changes during the progression from the early, pre-leukemic stage to full AML, as well as the effect of treatment on these changes and whether this has any prognostic value. The session also included a discussion of different disease conditions, such as AML, myelodysplastic syndrome, and the related aplastic anemia. Prof. Löwenberg explains that there is a lot of interest in this area due to the hope to treat patients better by taking into account the differences between them. Potential implications of understanding molecular heterogeneity are that we may be able to intervene in the developmental process and prevent the development of leukemia. Prof. Löwenberg also highlights the increased interest in inherited leukemia. While 10 years ago, AML was thought to be an acquired disease with no hereditary factors, new technologies enabling the determination of genetic mutations in leukemic and germ-line cells have led to the discovery of many hereditary components, with implications for the management of those patients with a predisposition for leukemia. A further topic at ISAL 2017 was chemotherapy resistance, as a new mechanism of resistance was presented, opening new avenues for interventions.