Today, we speak of “second generation chitosans” when we talk about well-characterized, pure chitosans with known properties and functionalities. They are clearly distinguished from the original “first generation chitosans”, which were varying mixtures of different undefined chitosans. At the same time, this indicates that the industry’s reservations caused by the unreliable properties of the raw, first generation chitosan are now no longer justified. The originally good reputation of chitosan (due to numerous advance praises) has been severely damaged by these problems, and the task now is to regain lost trust. This is why we and others have developed new, reliable analytical techniques in recent years that allow detailed quality control of chitosans. And we have used these well-defined second generation chitosans to investigate in molecular detail which chitosan does what. This is important, because even today, relatively inexpensive first generation chitosans dominate supplies worldwide. These are often good enough for technical applications such as water filtration, paper coating, or textile impregnation, for which the material properties of chitosan are crucial – and these are currently still the most important applications for the chitosan market, precisely because they are robust, can take large quantities of chitosan, and do not have extreme quality requirements. But these first generation chitosans are notoriously unreliable in applications based on the biological activities of chitosans. It is therefore of critical importance to differentiate the new, well-characterized second generation chitosans, which are now being offered by some suppliers in consistently high quality and also in sufficient quantities, from the older raw chitosan if we are to avoid another disappointment in life science product development. This is where our experience in biotechnological optimisation of chitosans steps in.