Some embodiments include memory cell structures. The structures include a vertical transistor having a bottom source/drain region electrically coupled to a first access/sense line, and having a gate comprised by a second access/sense line. The structures also include programmable material over the vertical transistor and electrically coupled with a top source/drain region of the vertical transistor, with the programmable material having at least two compositionally different regions. The structures also include an electrically conductive material over and directly against the programmable material. Some embodiments include memory arrays.