I am seeing an increasing number of patients that comes to my clinic with concerns about butt injection with fillers including silicone. I have also seen patient with silicone penis injection and silicone breast injections. Silicone is one of those fillers that appear to be increasing in use for the purpose of buttock augmentation. In the next few blogs I will discuss the properties of silicone, it mechanism of action and the impact it has in the body. In order to understand the role of silicone in soft tissue augmentation there are some basic concepts that are important to realize. Silicone oil by definition is any oil composed of polymers with different molecular weight of polydimethylsiloxane. Silicone with different length of the polymer affects it structural properties including its viscosity. (Thickness). Silicone is very common compound and can be found not only in plastic, greases for insulation, lubricants, binders etc. Moreover, we can find silicone in cosmetics, medication and food that we ingest on a daily basis. So basically silicone is everywhere. In the literature, silicone injection has been reported with not only industrial grade silicone but also medical grade silicone. The latter refers to silicone material that is pure in quality, sterile and of constant viscosity. But I heard that silicone is inert? Yes but inert does not necessarily means that is safe. Inert means that is immobile that it does not migrate. We have to take this definition into contest. Silicone might be chemically inert (having only a limited ability to react chemically; chemically inactive) but it is know that can degraded over time and we have seen this with the old silicone breast implants shell. In addition, it has been reported of migration of the product from the site of injection to other parts of the body. Just because silicone breast implants and other medical devices are currently safe to use for medical purposes like joints replacement, their composition is different than liquid silicone giving the product its unique structure. Liquid silicone can be problematic and the term inert might not be the right term to describe how it behaves once is injected in any part of the body. Liquid silicone injection has unique methods of interacting in the body and the buttock area for augmentation. In the next blog I will talk about how silicone interacts with any tissue including the buttock area.