Accumulated evidence indicates that low spatial ability makes a contribution, separate from levels of general or verbal intelligence, to the unlikelihood of students enrolling in, or succeeding in, STEM subjects. Further, there is a tendency for female students not to perform as well as males on some spatial tests, suggesting that this might be part of the reason for their under-representation in some STEM areas. However, the level of spatial ability has been shown to be related to both genetic and environmental factors, thereby suggesting that it can be improved with appropriate training. Here I look at some of this background and prior research, including training studies, in STEM subjects. Interestingly, as subject specific expertise develops, drawing on specific knowledge tends to replace need for spatial thinking, so it is the negotiation of any initial spatial barrier into a subject which is crucial. To effect this, I outline a relatively new spatial categorisation which could be valuable for STEM teachers as a framework to help them guide their students through the early spatial demands of their own teaching subject(s).