Multi-block copolymer. (a) Chromatin exists as a multi-blockcopolymer with flexible and stiff (coil-rod) chromatin. Stiff blocksself-interact creating an anisotropic crystalline phase (pile of red blocks).(b) These segregated blocks generate a symmetric microphase patternwhere the stiff phase (minor component) self organise in micro-spheres (redcircles) embedded in the major phase of flexible DNA (blue background).(c) The organization of the active chromatin microphase in the cellnucleus. Microspheres remain in a fixed position due to the balance of opposingforces. In the cell nucleus the existence of interphases creates an imbalancebetween the forces acting in opposing directions, with a net force pushing themicrospheres to the interphase. This explains the position of active chromatinat the edge of the condensed chromatin. (d) Model of self-organizationof active chromatin. Collinear active gene chromatin is hyper-acetylated whichresults in its self-interaction with neighbouring TUs. These interactions aredestroyed by the deacetylation of chromatin.