Photodissociation reactions play a vital role in initiating many chemical reactions in the atmosphere. This book presents a review on the photochemistry of alkyl nitrites, nitro compounds and carboxylic acid, with an emphasis on the recent progress in photodissociation dynamics by using laser induced fluorescent (LIF) technique. The use of artificial neural networks in predicting pollutants concentrations is also evaluated. Biodegradable materials are widely used in the biomedical field because there is no post-operative surgery after implantation. The use of nanofibres for tissue engineering is described, as well as the electrospinning technique as a way to fabricate controllable continuous nanofibre scaffold mimicking the ECM structure. Organochlorine pesticides, which have been used for decades as insecticides and for the control of vector-borne diseases, is looked at as well. Specifically, the use of organophosphorus pesticides as a replacement, their long-term persistance and their metabolites presented in water, sediments, soil and vegetables, as well as the modern strategies for the extraction of these compounds from environmental samples. Poly (ethylene terephthalate) (PET) is one of the most eco-friendly polymeric materials. It is largely collected and consumed in the form of PET bottles in Japan. This trend will most likely become a world-wide phenomenon, however, there are also problems attributed to this material recycling system. These problems, as well as the new technology used to improve processability for PET, are examined in this book. The innovative 3R Recycle-Reuse-Reduce AGROCARBON technology, which provides recycling of agricultural organic and mineral by-products, is also discussed, as well as the process that upgrades by-products to high added-value plant growth promotion and natural fertilization products for environmentally friendly vegetable cultivation.