This book covers Dr. Kumar's journey of his most relevant and important research that has beenfrequently cited by international communities in the field. His research journey is comprised offive different phases starting from the year 2000 to 2020, which are covered in five differentsections.Section I includes Dr. Kumar's research on engineering of mammalian cytochrome P450enzymes for their use in biotechnology, medicine, and bioremediation. In this section, Dr.Kumar describes the molecular basis of cytochrome P450 (CYP) engineering and providesseveral examples of engineered mammalian CYP enzymes for enhanced enzyme activity, stability, and tolerance to organic solvents. These engineered CYP enzymes could be developedfurther for industrial synthesis, medicine, and bioremediation. Although Dr. Kumar did notpursue this line of work later, the concept of engineering of CYP enzymes, especially bacterialenzymes, became extremely relevant and important for industrial synthesis of small moleculesand drug design. In fact, Dr. Frances Arnold from The Caltech University, who has been leadingCYP engineering since 1995, won the Nobel prize for her work in 2018.Section II includes Dr. Kumar's research on the role of CYP enzymes on smoking- and alcohol-induced HIV pathogenesis, response to antiretroviral therapy (ART), and NeuroAIDS. This lineof study is extremely relevant for HIV populations because the prevalence of alcohol drinkingand tobacco smoking is much higher in HIV populations than in normal populations. Throughthis research, Dr. Kumar established a link between CYP enzyme-mediated oxidative stress andHIV pathogenesis, which was further exacerbated in the presence of alcohol drinking andtobacco smoking. He also established the role of CYP enzymes on drug-drug interactionsbetween ART drugs and alcohol and tobacco constituents that potentially cause a reduced effectof ART drugs.Section III includes Dr. Kumar's research on the role of extracellular vesicles (EVs) or exosomeson cell-cell interactions. EVs or exosomes, being natural nanovesicles and secreted from allcells/tissues in the body, have been implicated in communication between organs when the cellsor body are exposed to external stimuli. Through his research, Dr. Kumar's group is the first oneto show the abundance of CYP enzymes in plasma-derived exosomes. In addition, they showedthe potential role of these and other enzymes in intercellular communication in the case of HIVpathogenesis and drug abuse. This ongoing project has immense value in understanding thebiology of EVs in terms of EV-mediated transport of drug metabolic and oxidative stress-relatedenzymes or factors in the body.Section IV includes the discovery of plasma EVs/exosomes or their components as potentialbiomarkers for HIV and drugs of abuse. The use of plasma EVs/exosomal biomarkers isrelatively easy and cost-effective for early diagnosis and prognosis of many diseases orconditions, especially related to the brain. In this section, Dr. Kumar describes the identificationof potential cytokines/chemokines and other proteins in plasma EVs that are altered under HIVand/or alcohol drinking and tobacco smoking conditions. These EV components, along withother newly discovered factors, have the potential to be developed as biomarkers for earlydiagnosis of HIV pathogenesis and HAND in HIV individuals and individuals who also drinkalcohol or smoke tobacco