Aging is inevitable, but it's certainly not consistent.We might think aging proceeds in a steady, linear fashion, with each day, week, and month marching us sedately into our Golden Years, but new research suggests that aging is more like a mosaic or patchwork quilt, stitched together by hormonal cues.A new study, published in Nature Aging, mapped structural changes across dozens of human tissues, and found that different parts of the body follow surprisingly variable aging schedules. Some begin changing rapidly in our 30s. Others remain relatively stable until around menopause in female bodies. And still others appear to go through two distinct periods of accelerated aging.In other words, there may be no single "aging process" happening throughout the body. Instead, different organs or bodily systems may have their own timelines –-and different organ systems can influence each other.To figure this out, the research team, led by computational biologist Sanju Sinha at the Sanford Burnham Prebys Medical Discovery Institute in California, developed a computational system called PathStAR to analyze the microscopic structure of tissues in routine pathology images. Rather than being trained to guess a person's chronological age, the system examined the physical architecture of tissue changes.The researchers applied the PathStAR analysis to images of more than 25,000 post-mortem tissue samples from 970 donors aged 21-70, covering 40 different tissue types."This is a public dataset used by hundreds of groups, but nearly everyone uses the molecular data," Sinha says, referring to the Genotype-Tissue Expression Project, for which the samples were collected."There are tens of terabytes of imaging data that have gone nearly untouched."