Iron sand is why the Third was the strongest in the history of the Sand. At one time it was a technique that Shukaku's host used. It's a technique the Third invented himself. He could mold the iron sand into various forms, changing it into weapons appropriate to the situation. The Third had a unique body that allowed him to change his chakra into a magnetic field. Human puppets made by Sasori retain the same chakra as when they're alive and can perform the same technique, unlike the regular puppets like his mother and father. Chiyo tells Sakura to leave since she doesn't stand a chance. But then Sasori attacks with the Kazekage puppet using Satetsu Shigure (iron sand rain). The mother puppet grabs Sakura out of the way while the father puppet protects Chiyo with a chakra shield. But iron sand has gotten into the joints of the puppets and now they're useless. Sasori attacks again with iron spikes from above and explosives from the kazekage puppet's chest. The mother puppet protects Saskura with a chakra shield. Chiyo's right arm is a puppet arm that acts like a shield. Her arm and the puppet now has iron sand in the joints and are no longer movable.

Flasback to photographing of Chiyo's son and daughter-in-law with baby Sasori. Then they leave Sasori to Chiyo and run off presumaly to fight. Later, Chiyo learns Konoha's White Fang has killed her son. Chiyo walks with Sasori, about 8 years old, and sees a kid who falls and cries. His parents comfort him. Sasori observes him for a while and then asks Chiyo to buy him some candy. Later Chiyo surprises Sasori with a little puppet that walks and bows. She offers to teach him the puppet control technique and takes him to a room with malfunctioning puppet parts. Sasori can use them to make his own puppet. Later that night, Chiyo sees him sleeping with his mother and father puppets. Next day, she sees him manipulating the puppets to embrace himself, but then he loses control and the puppets fall to the ground and break.

Chiyo detaches her puppet arm. Sasori release the iron sand again and forms a huge tetrahedron and block. Chiyo tells Sakura to run but she insists on staying and becoming Chiyo's puppet since the iron sand won't have effect on a puppet of flesh. But Chiyo has only one arm now. Metallic weapons won't work on Sasori, but Saukra has hand to hand fighting skills. She attacks and dodges the huge structures and knocks them back.

End: Sakura lectures on medical ninjutsu which requires specialized knowledge and excellent chakra control. Techniques include chakra scalpel and creation regeneration. Sakura smashes the camera in her enthusiasm to become like her master and Shizune.

Review: The Sasori flashback was very touching. He has such an angelic face!

Notes:
Only human puppets made by Sasori retain the same chakra as when they're alive and can perform the same technique.
The Third kazekage could change his chakra into a magnetic field and manipulate iron sand.
Satetsu Shigure = iron sand rain

Thoughts:
It’s unclear when Sasori’s parents dies. Either soon after birth or when he’s about 8.