Maturation of Pcs is concomitant with fissure formation. (a) At P0, anti-Calbindin immunostaining (red) shows that Pcs are organized in a multilayer throughout the Cb. In the principal (a1, a3) and non-principal (a2) fissures, the Pcs appear equally undeveloped, with small bodies and no apparent dendrites. (b) By P3, Pcs in the principal fissures (b1, b3) are arranged in a monolayer with distinct cell bodies and an apical dendrite (b1, arrow), whereas, in the non-principal fissure (b2), Pcs remain in a multilayer. The secondary fissure contains the most mature Pcs in the Cb, with dendritic branches beginning to form on the apical stem dendrite (b3, arrow). (c) At P5, Calbindin staining is more intense and more uniform. In all principal fissures, the Pc bodies have increased in size, and dendritic branches have begun to form (c1, arrow). In the secondary fissure (c3), Pcs are more mature than in other principal fissures, exhibiting more and longer dendritic branches (c3, arrow). Pcs in the non-principal fissure become organized into a monolayer (c2). (d) At P10, in all fissures, the number of secondary and tertiary dendritic branches in the Pcs continues to increase and the branches themselves continue to increase in length: (d1) preculminate fissure; (d2) prepyramidal fissure; (d3) secondary fissure. Scale bars: (a, b) 300 μm; (c, d) 600 μm; (a1-a3, b1-b3, c1-c3, d1-d3) 100 μm.