This document discusses individual heterogeneity (IH) in capture-recapture models from biological and statistical perspectives. It begins by introducing long-term individual monitoring datasets and some methodological issues when applying capture-recapture models to natural populations, including detectability being less than 1 and IH. The talk then explores several case studies related to accounting for IH, including detecting trade-offs using multistate models, describing senescence using mixture models, and quantifying the heritability of IH using animal models. Throughout, it emphasizes the importance of accounting for IH both statistically and biologically.