Body of Abstract: Climbers are abundant in hotspots of global change, such as tropical forests, in which they constitute a major functional plant type. The most common type of climbers are “twiners”, which wrap their main shoot around the host, climbing by means of exaggerated circumnutation, a revolving movement of the young shoots. Plant twining organs follow a helical path, generally of fixed handedness, as they climb a support. In the spiral1-like-4 spiral1-like-3Arabidopsis double mutant inflorescence stems grow in a helical fashion and twine around stakes, exactly as stems of natural climbing plants do; this mutant phenotype has been linked to skewed cortical microtubules. But how are microtubule arrays organized in stems of naturally occurring twiners? Here, using an integrative approach combining morphological and anatomical analysis, light and confocal microscopy, we investigated how changes in organ morpho-anatomy and microtubule orientation during stem development are associated with the establishment of the twining habit in a vining variety of common beans (Phaseolus vulgaris L.). We defined five distinct developmental stages, going from 9-days old seedlings to adult twined plants, that lead to the establishment of the twining habit. By analyzing the anatomy and microtubules orientation of internodes that participate in the circumnutational and twining movements across development, we show that at the tissue level no sign of twining or twisting is observed, however at cellular level skewed cortical microtubules orchestrated in the same direction seem to preponderate in twined stems, while varied orientation or transverse alignment prevail in other stages, thus supporting the canonical cell expansion model. This work further validates how microtubules determine cell shape, which in turn is translated to into organismal form. In the next steps we will investigate how microtubules behave during the turgor-driven non-permanent changes in cell size and shape that occur during circumnutation revolving movements.