This Fidabio handbook explains the role of Flow Induced Dispersion Analysis (FIDA) in biophysical characterisation for hit identification and validation in drug discovery. It compares the biophysical toolbox, addresses recurring screening problems (aggregation, stickiness, weak binders and reagent quality), and shows how FIDA measures molecular size, binding affinity and kinetics under native conditions — with worked examples across membrane proteins and GPCRs, de novo designed proteins, degraders and molecular glues, and biologics. It is an example of using FIDA to characterise interactions and sample quality across drug-discovery modalities.