Important biological differences between men and women exist – right down to the cellular level. Investigators from Brigham and Women’s Hospital and colleagues at Stanford University, McGill University and University of California, Berkeley wanted to determine if differences between male versus female cells may influence how well cells uptake nanoparticles – a key vehicle for imaging and targeted drug delivery applications. The team demonstrated that cell sex considerably influenced cellular uptake of nanoparticles and found that cells from men and women responded differently to reprogramming techniques used to enhance the ability of the cells to differentiate into a greater variety of cell types. Their results, published this week in ACS Nano, may help researchers more safely and effectively produce nanomedicines that take sex into account.