The detailed processes in the Claisen rearrangement were observed. The process was vibrationally excited in the electronic ground state by a stimulated Raman process using a 5-fs pulse. The Claisen rearrangement was found to follow a three-step pathway. At first, the C-4-O bond is weakened to generate a bis-allyl-like intermediate. Next, the formation of a weak C-1-C-6 bond results in the generation of an aromatic-like intermediate. Finally, C-4-O breaking and C-1-C-6 formation occur simultaneously to generate the product.