Core-shell nanoparticles displaying spin crossover (SCO) effect on the shell and/or on the core are studied using Monte Carlo simulations of an elastic microscopic Ising-like model. In this Letter we demonstrate that the SCO transition temperature can be controlled by adjusting the width of the shell and the width of the core as well as the misfit between the lattice constants. An original coupled system with a SCO active shell and an active core with another SCO material is proposed. Inducing the transition of the core by the spin transition of the shell results in a hysteresis in the thermal spin transition of the shell. This new type of memory effect in SCO compounds is based on the engineering of particle morphology. (C) 2014 Elsevier B. V. All rights reserved.