Carbon nanotubes (CNTs) were first specifically identified and described in 1991.1 These nanoscale materials have since been widely used in a variety of fields due to their extraordinary properties, including high surface area, high mechanical strength, electronic properties, and excellent chemical and thermal stability. CNTs have also been developed and explored for a wide range of applications including in biomedicine, as biosensors, tissue engineering scaffolds, and drug delivery systems. The interaction between CNTs and mammalian cells was first observed by Pantarotto and co-workers in 2003. Chemically functionalized singlewalled CNTs were studied to report internalization by cells. Since then, more experimental techniques, materials, and cell types have been studied to identify the interaction between CNTs and cells in vitro. A variety of investigations are currently underway to study the interaction between biological systems and CNTs.