The ability to determine protein structure using crystallography has led to a massive improvement for the ability to investigate, describe, and influence the the function of proteins performing very diverse functions. However, it has been found that proteins in solution are dynamic, and can contain flexible domains. Small-Angle X-ray Scattering (SAXS) is an insolution technique well suited to probe the in-solution structure and flexibility of proteins. Time-resolved studies of structural changes in proteins has become possible using fast mixing methods in combination with synchrotron SAXS. The aim of this thesis was to identify, develop, and characterize a model system to investigate the capabilities of such setups. A long-acting insulin analogue was investigated using static SAXS measurements, and it was found to self-assemble into very long rod-like structures upon a change in salinity of the buffer. It was subsequently subjected to time-resolved investigations using two different fast mixing methods: stopped-flow mixing and laminar flow diffusion based mixing using a microfluidic mixer. The stopped-flow investigation of lithocholyl insulin was successful, and high quality data was obtained. The self-assembly was characterized, and it was found to take place as two separate processes described by two very different time-constants. A rapid growth phase from ∼5-241 ms, followed by a slower more subtle elongation phase for the remainder of the time-window. The lithocholyl insulin model system was then subjected to investigation using the all-quartz microfluidic laminar-flow mixer. The experiment was a success, and a high quality time-resolved dataset was obtained. The fast process was probed, and the modelling revealed that kinetics had successfully been captured using the diffusion based mixer. t0 of the reaction time was calculated theoretically, and confirmed by comparison with the earlier stopped-flow experiment. Furthermore, Bovine Serum Albumin (BSA) and pH-induced unfolding was investigated using the same setup, and it was confirmed that the setup is compatible with more subtle intramolecular changes to protein structure.