Chemical reactions at the fluid-rock interface play a key role in a wide range of processes and applications ‎in the subsurface, including soil remediation, water treatment, and geological CO2 storage among others. ‎The kinetics of these reactions are generally modelled by assuming that reactants in the fluid phase are ‎well-mixed at the pore scale. Recent findings by optical imagery, though, show that steady laminar flow in ‎transparent beads produces chaotic microscale trajectories, akin to turbulent flow but at low Reynolds ‎numbers, questioning the well-mixing assumption in the current paradigm of reactive transport modelling. ‎However, proving the existence of chaotic mixing in porous rocks has yet remained unresolved. Here, we ‎present preliminary results on the existence of chaotic microscale trajectories, i.e., fluid stretching and ‎folding, not only in bead packs but also in natural rocks by conducting 3D (relatively) high-resolution X-‎ray tomography. Using a purpose-built core holder and highly permeable porous media enabled us to reach ‎very high Peclet numbers during the co-injection of two miscible highly viscous fluids. The high Peclet ‎numbers are essential to image chaotic trajectories in the pores at the interface between the two fluids ‎before molecular diffusion obscures the deformation of fluid fronts. The existence of such trajectories leads ‎to substantially enhanced microscale concentration gradients that could result in chemical reaction rates ‎deviating from those predicted by reactive transport models. Insights gained from this study, combined ‎with fast, high-resolution, low-noise synchrotron imaging will allow us to develop an in-depth ‎understanding of mechanisms and factors controlling chaotic mixing and accordingly derive kinematic ‎models for improved modelling and prediction purposes.‎