Textiles with transformative behaviour transform when exposed to a stimulus. Woven flat, they take on new forms as they are activated. Their form is emergent, a property of the interaction of material, structure, and environment. Textiles with transformative behaviour are composed of simple materials – conventional textile fibres – hierarchically organised through yarn, weave, and textile structure. Their active yarns respond to stimuli from the environment, translating free energy into movement, reorganising the textile into a minimum energy state. This process of morphogenesis unites material and formation: it is the very specificity of material in its structure in an environment that generates form.Through practice-based research in the field of textile design, experimental samples have been woven and analysed in order to understand the transformative forces in the textiles. Two techniques for producing transformative behaviour have been identified and ex-plored: shrinking/resisting and twisting. Shrinking yarns include elastics and thermoplastic polyester yarns, while the resisting yarns are stiff but pliable monofilament or paper yarns. Combining shrinking and resisting yarns in multi-layer weave structures produces voluminous three-dimensional form as the resisting yarns deflect from the textile plane reshaped by the active shrinking yarns. The twisting technique makes use of the hygromorphic properties of high-twist linen yarn as weft. Transforming in response to mois-ture, this natural fibre produces multiple non-linear transformative behaviours. These have been explored in depth to produce a design model identifying the design variables influencing three transforma-tive behaviours: rolling, pleating, and texturising.This foundational research is aimed at other textile designers working in weaving. It is intended to provide examples and tools for designing textiles with transformative behaviour, with potential appli-cations within and beyond textile design. It challenges top-down de-sign approaches and conventional perspectives of textiles as 2D and static, proposing new possibilities for designing adaptive, sustainable textile systems.