Here, I present a recent critical analysis of standard length-based methods and a new generation of approaches, models and new robust tools. All population models, stock assessments, food web models, End-to-End models and coupled socio-ecological models rely on basic data, such as growth and mortality. However, the uncertainty inherent to growth and mortality estimates has hitherto rarely, if ever, been questioned and thoroughly analyzed. Examples of populations of mangrove crabs (Cardisoma guanhumi), white clams (Abra alba) and synthetic population data are shown. New methods based on bootstrapping (ELEFAN_boot) and permutation (perLEFAN) are being implemented within the fishboot package. New, simple, size-spectra tools and size-based Bayesian tools are emerging. With these new approaches and toolboxes, we are at the very beginning of a long journey towards reliable length-based models and methods.