According to the current fashion, curls can be a blessing or a curse: people often spend a lot of money to tame unmanageable curls, or carve luxurious waves. However, despite decades of research, it is still unclear why the hair will naturally curl. Duane Harland, from AgResearch, New Zealand, says there are two competing theories. Since a single hair is made up of two different cell types-the neighboring cells ( Filled with parallel collagen fibers) Positive cortical cells ( Fill in with twisted collagen fibers) -A theory holds that longer positive cortical cells are lined on the outside of the curve, and there are collateral cortical cells on the inside. Another theory is that there are more cells on the outside of the curl, because the cell division on that side of the follicle is more, increasing the number of cells in the curve outside the curl. But most of these theories have very limited or indirect evidence to support them, Haran said. Jolon Dyer and Stefan Clerens have worked with Japan\'s Kao Corporation cosmetics company to learn more about the structure of human hair and work with Shinobu Nagase, takitou and Koike are going to solve the tricky problem of what makes hair curl. Human hair, however, is too rough to analyze its cellular structure, so the team switched to fine-curled merino wool. They explained that the chemistry, structure and growth of all hair are essentially the same, so the lessons learned from wool will also apply to human hair. Knowing the exact origin of the merino sheep using wool in the study, David scobi cut several full length locks from the winter clothes of each animal before Haran, james Vernon and Joey Woods spent hours carefully cleaning and preparing for more than 700 hours. 5 cm pieces from the bottom of a single fiber. \"We have to go out of our way to make sure that we measure the natural curvature programmed during fiber development, not the curvature that is strong in the wool placed on the back of the sheep or during washing and processing,\" he said. As a result, the fibers dry on the vibrating surface to ensure that they do not show any additional distortion. Harlan describes how to manipulate the fragments on a microscope slide to make the nerves stable. \"Catching the clips with fine tweezers is not an option as they are easily damaged . . . . . . So we use the static force at the tip of the fine tweezers to accurately locate them. The team then measured the curvature of each wool fragment before staining and transferred it to a co-Focusing microscope to reveal the curled cell structure. After several months of counting and measuring the cells inside and outside of each curl fragment, the team can see that the curve is lined up with shorter cortex cells inside, the longer positive cortex cells are located on the lateral side of the curl. Therefore, curl is produced by arrangement of different cell types, rather than by cells that split more frequently on one side of the follicle to produce more cells on the outside of the curl. We have made it clear that cell type and cell length are important, and so should human hair, Haran said. The global hair care market is estimated to be worth more than $85 billion, and the team is optimistic that their new findings will help design new hair care products. Haran said an improved understanding of how hair features affect their appearance and physical features is an essential background.