PDF of article embargoed by the publisher until march 2019 ; PDF of article embargoed by the publisher until march 2019 ; PDF of article embargoed by the publisher until march 2019 ; PDF of article embargoed by the publisher until march 2019 ; Vertebrate hard tissue biologists study the surface and below-surface microanatomical features and compositional characteristics of bones and teeth of the skeleton (fish scales also deposit calcium phosphate and calcium carbonate into their structure, and we include them among the tissues we study). The variability in bone and tooth histology rivals that of all other organ systems, making it an ideal tissue for understanding the development, function, and physiology of organisms. What is more, in deference to soft tissues, bones and teeth survive as fossils, permitting all that we can know from the skeleton about an organism living today to be extrapolated to animals living millions of years ago.