Derald Wing Sue et al. (2007) posit that micro-aggression racism is:
a contemporary form of racism that is invisible, unintentional, subtle in nature, and typically outside the levels of conscious awareness, but it creates a hostile and invalidating climate nonetheless. According to Sue and Colleagues, the cumulative of micro-aggressions may be just as harmful as outright racism, although more research is needed in this regard.
Source: Ghaffar-Kucher, A. (2011). The religification of Pakistani-American Youth. American Educational Research Journal. Pg. 26.