The mechanics of complex structures is determined by the way force distributes through the network of molecular connections. How can the force-bearing elements of a structure be detected? We recently developed a technique termed Force Distribution Analysis (FDA), based on standard Molecular Dynamics simulations, to reveal the propagation of stress through a molecular structure. FDA is the atomistic-scale analogue of Finite Element Analysis for macroscopic structures. I will describe the concept of FDA, and its ability to bridge different length scales. Two recent applications will be discussed, namely silk fiber mechanics and the effect of flaws in nanocrystals as they occur, among others, in mother-of-pearl.