In the 60′s the creature inside the Dalek remained a mystery. In the first Dalek story all that was shown was a claw hand sliding out from under a blanket. Later in the 60′s the Dalek appeared as a mutated ‘blob’. In the 80′s the same idea was applied, a green mutation. Between 1963 and 1988 the only time the inside of a Dalek was shown was when a Dalek had been destroyed, so the true living Dalek mutation wasn’t fully shown until 2005.
In the first Dalek story the Doctor, Ian, Susan and Barbara captured a Dalek and removed the mutated creature inside and wrapped it in a blanket. Only the claw below was shown. Ian and the Doctor opened the top of the Dalek so that Ian could get inside, Ian controlled the Dalek allowing them all to escape.
In The Power of the Daleks a Dalek factory is shown where Dalek mutants are fitted into their casings.
In Ressurection of the Daleks we got to see the remains of a Dalek after a group of humans had blown it up removing the head. In Revelation of the Daleks Davros was turning Humans into Daleks (below middle).
Like in Ressurection of the Daleks all we got to see were the remains of the exploded Daleks, one Dalek remained active, a claw reached out and grabbed the Doctor by the neck.
The first time we got to see the inside of a Dalek clearly was in the episode Dalek where the casing opened to reveal the mutated Dalek.
In The Parting of the Ways the Emperor of the Daleks creature was clearly visible in a glass casing underneath the dome.
Dalek Sec appeared more greener than the previous Daleks. The bottom half of his casing also opened. The picture on the far right shows his Human form.
Dalek Caan flew back into the Time War to save Davros. During the process Dalek Caan became insane.