An intracellular structure that can catalyze gamma-tubulin-dependent microtubule nucleation and that can anchor microtubules by interacting with their minus ends, plus ends or sides. [ http://www.ncbi.nlm.nih.gov/pubmed/17072892 http://en.wikipedia.org/wiki/Microtubule_organizing_center https://www.worldcat.org/search?q=bn%3A0815316194 http://www.ncbi.nlm.nih.gov/pubmed/17245416 ]