Isolated grana in surface view

Thylakoids of grana are disk-like

A surface view of whole isolated grana from a chloroplast as seen with surface replication for transmission electron microscopy.

Note that the grana appear as disk-like structures in a cluster, and they are all of similar size and diameter. They are held together by inter-grana thylakoid membranes.

Illustration from: Jensen & Park, 1967, Cell Ultrastructure, Wadsworth Publishing Co., Inc.