Introduction: Aging followed by death is an inevitable fate in most organisms including human. Each species exhibits its own characteristic life history of aging and death. We have been studying the regulatory mechanisms of aging in plants and animals from the comparative aspects. I will first introduce the overall research areas related to aging mechanisms in the Center for plant aging research, IBS and in the comparative aging research group at Dept. of New biology, DGIST. Plant aging: Plants undergo aging and death in a species-specific manner with highly diverse life history strategies. Our group has been studying the molecular mechanisms of aging and death in plants over two decades, revealing that aging and death in plants are highly regulated at the chromatin, transcriptional, post-transcriptional, and epigenetic levels. I will present our new progress in revealing regulatory mechanisms of plant aging and senescence, including network-level regulation of aging and interaction of circadian clock with aging regulator in Arabidopsis. Comparative aging in plants and animals: Plant aging and senescence are highly regulated developmental process, and how to age not just when to die is critical for fitness. We have adopted this concept in the study of animal aging, mostly at RNA-based control of aging. I will present some key aspects of our age-dependent transcriptome profiles from plants and animals. A distinctive feature of plant transcriptome is that the transcriptome is highly coordinated until the last stage. The transcriptome analysis also show that plants and animals employ various types of regulatory RNAs including miRNAs. We have been elucidating the regulatory roles of miRNAs in aging process. Our interest in the regulatory role of a miRNA in aging stemmed from our previous discovery in Arabidopsis. We will present our recent result on the pro-aging role of age up-regulated miRNAs in mouse brains. Modifying aging process in plants is readily feasible. Toward modification of the aging process in animals, we previously showed in mice that old pancreatic islets transplanted into young host can be readily rejuvenated. We will also discuss our effort to search longevity securing genes in mouse and C. elegans. Cloud biochemistry: Biological reactions occur in small confined spaces. Yet, most of chemical reaction properties have been characterized in bulk solution. We will present our discovery that biochemical and chemical reactions in cell-sized water mist (or micro-droplets) can be accelerated by order of 3 to 6, which we named “cloud chemistry.