text: A<unk>  is a dynamic, actin-supported extension of a developing axon seeking its synaptic target. Their existence was originally proposed by Spanish histologist Santiago Ramón y Cajal based upon stationary images he observed under the microscope. Neuronal<unk> s are situated on the very tips of nerve cells on structures called axons and dendrites. The most crucial roles of the neuronal<unk>  are to explore its surroundings ultimately establishing synaptic contacts.
option_0: Growth cone
option_1: Articular processes
option_2: Optic stalk
option_3: Ganglion
option_4: Atlas 
option_5: Nucleohyaloplasm
option_6: Ependyma
option_7: Danger space