What is the number 1 product for thinning hair?

I'm curious, can you tell me what the number one product is that people recommend for thinning hair? I've heard a lot about different treatments and shampoos, but I'm not sure which one is the most effective. Is there a particular brand or ingredient that stands out as the best option for those looking to address hair thinning? I'd appreciate any insights you might have on this topic.