Peds are base of soil and each individual unit of soil is called PED. Ped doesn't have to be parallel to bedding and it is related more to vegetation. Peds can have internal structures and clays can form on these structures. Sizes vary from 1 mm granules to 10 cm prisms.
Various types of peds include:
Prismatic Peds: 1 cm to 10 cm diamater. Flat to rounded vertical faces. Units are longer vertically. Characteristic of B-Horizon. Vertical cracks result from freezing & thawing & downward movement of water.
Platy Peds: Units are flat and plate like. Generally horizontal and found in leached soil horizons and C, E, B & K-horizons.
Granular Peds: Units are approximately spherical or polyhedral and bound by curved or very irregular faces that are not clasts of adjoining peds. They look like cookie crumbs, are usually organic rich and common in A-horizon soils. Also associated with grass.
Columnar Peds: Vertical colums of soil that have a salt cap at the top. Found in arid climates. Units are bounded by flat or slightly rounded vertical faces. Rich in swelling clays such as smectites. This structure is difficult for plants roots to penetrate.