Propagating cannabis from small pieces of tissue on sterile media rather than from cuttings in a tray: media recipes, hormone ratios, contamination control, acclimatisation back to soil, and the meristem work used to clean a line of virus and viroid.
The reason to do this rather than take cuttings is storage and sanitation. A library of cultures occupies a shelf instead of a mother room, cultures can be held in slow growth for long periods, and meristem culture is the established route to recovering a cultivar from a systemic infection that no spray will touch.
Two things decide whether a laboratory works. Sterility is the entire discipline, and almost every failure is a contamination event traced back to technique at the bench rather than to a recipe. And acclimatisation is the step people underestimate: a plantlet grown in high humidity on sugar has poorly functioning stomata and no working root hairs, so moving it out too fast kills weeks of laboratory work in an afternoon.
Where to start
Related elsewhere on the forum: Mother Plants and Cloning: Your Genetic Vault in Advanced Techniques.