In the present chapter several aspects of kainic acid action on the rat brain structure were presented. Specifically, using histological, electronmicroscopical and two-photon microscopical approaches, we elucidated: (i) The pyramidal and interneuron cell loss in different layers of hippocampal CA1 and CA3 areas as a result of kainic acid-induced status epilepticus; (ii) The ultrastructure of neurons, synapses, glial cells andneuropil of hippocampal CA1 area provoked by kainic acid-induced status epilepticus; (iii) The effect of different concentrations of kainic acid on dendritic spine motility of living hippocampal neuron at the different stages of development; (iv) The effect of different concentrations of kainic acid on the density of various types of spines (filopodia, mushroom and stubby spines, alongated, enlarged or thin formes with head or without) in living hippocampal neuron at different stages of development. In all cases several modifications were revealed. Possible consequences of such modifications are discussed.