Advances in cataloguing and culturing global microbial diversity have renewed the interest in so far uncultured taxa. The often-cited assumption that only 1% of all microorganisms can be cultured has been challenged by previous work suggesting that a high proportion of bacteria across different environments has been cultured already. However, Thrash and colleagues now revisit these and additional data and point out technological and conceptual pitfalls that might lead to an overestimation of the cultured proportion, for example, primer and database biases. They conclude that the majority of bacteria and archaea is still uncultured and argue “that it is impossible to know whether a microbe is culturable until it has been cultured” and that the term ‘unculturable’ should be avoided. The authors note that there are a few studies and environments such as the human gut in which culturing efforts have yielded higher proportions, and thus culturing uncultured taxa remains a priority.