dendritic spines are small with spine head volumes ranging 0.01 μm to 0.8 μm. spines with strong synaptic contacts typically have a large spine head, which connects to the dendrite via a membranous neck. the most notable classes of spine shape are "thin", "stubby", "mushroom", and "branched". electron microscopy studies have shown that there is a continuum of shapes between these categories. the variable spine shape and volume is thought to be correlated with the strength and maturity of each spine-synapse.