Just before the execution the instruction is separated into several pieces. The execution isn't always fast and painless. On crude hardware the execution of a complex instruction can take as long as 150 clock cycles. Scientists are working on shorter execution times. It is more humane to use software which minimises the executions.
Modern machines use several units to execute multiple instructions simultaneously.
This way it is possible to execute several hundred million instructions per second. The time is near when there will be no more instructions to execute.