Ones that follow people over an extended period of time, usually several or more years, to examine patterns involving earlier and later experiences and development. The US is replete with such studies.
See Attrition, Autoregressive series/model, Cohort, Cohort effect, Compound symmetry, Cross-lagged correlation/regression model, Early Childhood Longitudinal Studies (ECLS), Follow-back design, Latent growth model, Linear growth model, Longitudinal design, Longitudinal-exoperimental studies, Microgenetic method, Mid-growth spurt, Motor Performance Study (Michigan State University), Multiple cohort study, National Child Development Study (NCDS), National Educational Longitudinal Surveys (NELS), National Institute for Child Health and Human Development Study of Early Child Care (NICHD-SECC), National Longitudinal Study of Adolescent Health (AddHealth), National Longitudinal Survey of Children and Youth (NLSCY), New York Longitudinal Study (NYLS), Panel studies, Period effect, Person-centrered approaches, Prodiction and retrodiction, Sleeper effect