The scientists studied how cryoprotectant (a substance that helps preserve cells during freezing) and ice are distributed in frozen plastic straws used for storing sperm, eggs, and embryos. They used a tool called Raman spectroscopy to analyze these straws filled with cryoprotectant solution and frozen at different rates. The results showed that the cryoprotectant was not evenly spread along the straw, with more of it found at the bottom where embryos or eggs are usually placed. This uneven distribution could affect the freezing process. The study suggests that factors like cooling speed and ice formation temperature may influence how the cryoprotectant is distributed within the straws, potentially impacting the success of preserving embryos and eggs for future use.