How acentrosomal microtubules become organized into particular patterns in the absence of a centralized microtubule organizing complex remains a mystery. The plant cortical microtubule cytoskeleton is an ideal model system to address this question. Plants naturally lack centrosomes and their interphase microtubules form wonderfully ordered arrays at the cell cortex that can be easily imaged at high resolution. We have proposed a self-organizational model for cortical microtubule array formation based on our observation that interactions between cortical microtubules lead to specific outcomes depending on the angle of the microtubule interaction. To understand how interactions between cortical microtubules shape array formation, we are using a combination of single molecule imaging, molecular genetics and computer simulations to study how activities at the molecular level result in microtubule organization at the cellular level.