The particle (1) is suitable for the manufacture of an implantable soft tissue engineering material and comprises: a three-dimensionally warped and branched sheet (2) where (i) the three-dimensionally warped and branched sheet (2) is made from a biocompatible material having a Young's modulus of 1kPa to 1GPa; (ii) the three-dimensionally warped and branched sheet (2) has an irregular shape which is encompassed in a virtual three-dimensional envelope (3) having a volume VE; (iii) the three-dimensionally warped and branched sheet (2) has a mean sheet thickness T; iv) the three-dimensionally warped and branched sheet (2) has a volume VS; (v) the particle (1) has a Young's modulus of 100Pa to 15kPa; and (vi) the particle (1) further comprises a number of protrusions (4) where the three-dimensionally warped and branched sheet (2) reaches the envelope (3); (vii) the particle (1) has a number of interconnected channel-type conduits (5) defined by the branching of the sheet (2) and/or by voids in the sheet (2); and (viii) where the conduits (5) have (a) a mean diameter DC; and (b) an anisotropicity index of 1.01 to 5.00.