There is an urgent need for new tools to understand the structure, recognition, metabolism, and biosynthesis of glycans as well as the production of biologically important glycans and glycoconjugates. With the discovery of glycoprotein synthesis in bacteria and functional transfer of glycosylation pathways between species, Escherichia coli cells have become a tractable host for both understanding glycosylation and the underlying glycan code of living cells as well as for expressing glycoprotein therapeutics and vaccines. Our group has harnessed natural biological pathways and engineered synthetic designer pathways in bacteria for making complex glycans and conjugating these to lipids and proteins. Our lab’s efforts have resulted in the transformation of bacteria and their cell-free extracts into robust platforms for scalable, bottom-up production of complex glycoconjugates by design.