Lignin, along with cellulose and hemicelluloses, is a structural component of vascular plants. The material properties of lignin make plants to withstand mechanical stress, biological attacks and even fire. In order to obtain cellulose, wood chips are freed from lignin and this material is then burned to recover pulping chemicals. There is a surplus of lignin that cannot be burned anymore and this material can be used as an ingredient in biocomposite materials. It is interesting to incorporate lignin in composites owing to the properties it displays in plants. In this book the modification of lignin and polypropylene with cold plasmas is presented as a strategy for compatibilzation of polar lignin with the non-polar character of polypropylene. Surface modification of polymeric materials through plasma techniques is envisioned as an interesting option for preserving the bulk properties of materials and to avoid large volumes of reactions required for their modification by traditional wet chemistry.