1. Introduction  
2. Sample, Observations, and Data Analysis  
2.1. Double-Barred Galaxies in TIMER  
2.2. Observations and Data Reduction  
2.3. Data Analysis  
3. Results  
3.1. Mean Stellar Population Properties in Inner Bars  
3.2. Profiles Along the Inner Bar Major and Minor Axis  
4. Discussion  
4.1. Stellar Populations in Bars, Inner Bars, and Their Star Formation Deserts  
4.2. Flat Population Gradients Along Inner Bars: Orbital Mixing  
4.3. Young Ends of Inner Bars: Orbital Age Separation  
5. Summary and Conclusions