Absolutely, expired makeup can serve as a great educational tool, especially in the fields of cosmetic science, chemistry, and microbiology. Here are a few ways how:

1. **Understanding Chemical Stability**: Over time, the chemical composition of makeup changes. This can be due to oxidation, exposure to heat, or other environmental factors. By studying expired makeup, students can learn about the stability of various compounds and how they degrade over time.

2. **Microbial Growth**: Expired makeup can become a breeding ground for bacteria and fungi. This provides an opportunity to study microbiology, understand different types of microbes, and learn about the conditions that favor their growth.

3. **Preservation Systems**: The preservation system in makeup is designed to prevent microbial growth. However, these systems can fail over time or with misuse (like using dirty applicators). Studying expired makeup can help understand the effectiveness of different preservatives and how they can be improved.

4. **Product Formulation**: By analyzing the changes in expired makeup, students can learn about the original formulation and how different ingredients interact with each other. This can be useful in developing new and improved formulations.

5. **Sensory Changes**: Expired makeup often changes in smell, color, and texture. These changes can be studied to understand the sensory aspects of cosmetic science.

6. **Safety and Regulations**: Expired makeup can pose health risks, which makes it a good tool to discuss the importance of safety regulations in the cosmetic industry.

Remember, while expired makeup can be useful for educational purposes, it should never be used on the skin due to the risk of infections and other skin issues.