Analyzing continuous conformational transitions of biomolecular complexes allows to determine the dynamics of the complex and is a key to understanding its functions and structure-based drug development. We present an original approach for extracting atomic-resolution landscapes of continuous conformational variability of biomolecular complexes from cryo electron microscopy (cryo-EM) single particle images. This approach is based on a new 3D-to-2D flexible fitting method, which uses molecular dynamics (MD) simulation and is embedded in an iterative conformational-landscape refinement scheme. This new approach is referred to as MDSPACE, which stands for Molecular Dynamics simulation for Single Particle Analysis of Continuous Conformational hEterogeneity. We describe the MDSPACE approach and show its performance using a synthetic dataset of ABC transporter and an experimental dataset of yeast 80S ribosome.