Two similar, yet unequal minimum-energy conical intersections (MECIs) have been found along this route, marked in Figure (a) as MECI out and MECI in . Both characterize with perpendicular rotor orientation and strong pyramidalization of the top carbon atom participating in the C=C bond, but differ in the direction of this pyramidalization, with MECI in showing slightly lower adiabatic energy of 3.041 eV vs. 3.120 eV for MECI out . Both these energies lie well below the initial S 0 → S 1 excitation energy, making the identified MECIs energy-accessible. Eventually, it can be expected that, once the system arrives in their vicinity, efficient relaxation to the ground electronic state should take place, similarly as in the second-generation motors. After landing on the S 0 PES, the motor can either come back to the starting S isomer, or continue rotation towards the M form (right panel of Figure ). In the latter case, the vibrationally hot system encounters only minimal energy barrier of about 110 meV (2.5 kcal/mol) to complete the final, so called 'thermal' step of the rotation cycle, reaching the product S form, chemically equivalent to the starting point. The expected, only short-time population of the metastable form shows some resemblance of the PFCN operation cycle to that of the two-stroke second-generation motor proposed recently by Olivucci et al. Having said all this, we would like to draw the reader's attention back to the problem of the system chirality. The reaction path shown in Figure (a) and in the right panel of Figure illustrates the clockwise rotation of PFCN, sequentially populating the S R → M S → S R structures.