Neural circuit assembly features simultaneous targeting of numerous neuronal processes from constituent neuron types, yet the dynamics is poorly understood. Here, we use the Drosophila olfactory circuit to investigate dynamic cellular processes by which olfactory receptor neurons (ORNs) target axons precisely to specific glomeruli in the ipsi- and contralateral antennal lobes. Time-lapse imaging of individual axons from 30 ORN types revealed a rich diversity in extension speed, innervation timing, and ipsilateral branch locations and identified that ipsilateral targeting occurs via stabilization of transient interstitial branches. Fast imaging using adaptive optics-corrected lattice light-sheet microscopy showed that upon approaching target, many ORN types exhibiting "exploring branches" consisted of parallel microtubule-based terminal branches emanating from an F-actin-rich hub. Antennal nerve ablations uncovered essential roles for bilateral axons in contralateral target selection and for ORN axons to facilitate dendritic refinement of postsynaptic partner neurons. Altogether, these observations provide cellular bases for wiring specificity establishment. [Display omitted] • Establish an explant system for time-lapse imaging of fly olfactory circuit assembly • Image single ORNs from 30 types and characterize heterogeneous targeting behaviors • Fast imaging of ORN terminals reveals novel structure and cytoskeletal organization • Antennal nerve severing reveals requirement of bilateral ORNs in correct targeting Systematic time-lapse imaging of ∼30 olfactory receptor neuron types during circuit assembly reveals dynamic process of axon guidance and target selection. [ABSTRACT FROM AUTHOR]