According to examples, a three-dimensional (3D) fabrication system may include a controller to identify a feature of an object to be fabricated and based on the identified feature having a size that is smaller than a predefined size, determine a thermal support for the identified feature. The controller may also control fabrication components to form, through application of energy, the determined thermal support from a first set of particles, form an intermediate section adjacent to the formed thermal support from a second set of particles, and form, through application of energy, the feature adjacent to the intermediate section from a third set of particles, in which heat from the thermal support is to reduce a thermal bleed rate of the third set of particles.