Birth represents a transitional point in time – a static moment that borders a time of complete dependency and the march toward independence. This chapter reviews some basic concepts of vertebrate development and histology. Of particular relevance are tissue changes that reflect differentiation of mineralized tissues: skeletogenesis and odontogenesis, beginning with changes to the primitive connective tissue (mesenchyme). Viewed by microscopy, mesenchyme condenses prior to differentiation into cartilage, bone or tooth germs. Most mesenchymal condensations for the skeleton form during the embryonic period, but they continue to appear during the fetal period or postnatally for some structures (e.g., successional teeth). Most growth of the skeleton occurs during the fetal and postnatal periods. Mineralized connective tissues have different available growth processes. The contributions of appositional growth (new matrix is added to existing matrix), interstitial growth (cell replication and matrix production within existing tissue), and bone modeling (selective osteoclastic and osteoblastic activity) are discussed according to types of bones and skeletal regions.