Structure development is a key issue in polymer processing, with a view to master the final properties of the products (mechanical, optical, etc.). Among the phenomena involved, crystallization plays a major role. It generally occurs in complex, inhomogeneous and coupled mechanical (flow, pressure), thermal (cooling rate, temperature gradient) and geometrical (surface of processing tools) conditions. A first route to understand structure development is to design model experiments to isolate the specific influence of a given parameter. The emphasis will be laid here on: (i) the influence of shear flow through rheo-optical measurements. (ii) the influence of high cooling rates. High cooling rates are obtained with a modified hot stage named CRISTASPEED (up to 2000 °C/min) [1] and comparison has been made with DSC experiments using conventional as well as flash DSC. (iii) the influence of high pressures. An original cell named CRISTAPRESS (up to 200 MPa) [2] has been especially designed for high-pressure experiments. Numerical simulation is also a useful tool to understand and predict the coupled phenomena involved in crystallization. Based on Avrami’s ideas and equations, a general differential formulation of overall crystallization kinetics has been proposed [3]. It is able to treat both isothermal and non-isothermal cases, and has been extended to take into account flow as well as surface (transcrystallinity) effects. . [1] S.A.E. Boyer et J.M. Haudin, Polym. Test., 29, 445-452 (2010) [2] S.A.E. Boyer, F.E.J. Fournier, Ch.-A Gandin et J.M. Haudin, Rev. Sci. Instrum., 85, 013906 (2014) [3].J.M. Haudin et J.L. Chenot, Intern. Polym. Proc., 19, 267-274 (2004)