http://www.google.co.nz/logos/2010/xraydiscovery2010-ps.gif

http://www.google.co.nz/search?q=X-Rays&ct=xraydiscovery2010-ps&oi=ddle

In fact, 'X-Rays'.

Now we know how the logo looks on the inside :-), with a rubber duck!

Thanks Google, waiting has been worth of it! :)

the first x-ray or röntgen image:
http://upload.wikimedia.org/wikipedia/commons/e/e4/Roentgen-x-ray-von-kollikers-hand.jpg

Wasn't this the first one? Of his wife hand made taken on 22 December 1895. The image above was taken on 23 January 1896.

http://upload.wikimedia.org/wikipedia/commons/6/6e/Anna_Berthe_Roentgen.gif

why is there a secret '69' on the background of the two 'o' letters?

Hahahaha, yes noticed that too, but I don't think that it was on purpose given the fact where 69 stands for.......

Is that a pigeon in the small g?

WebSonic
the image i posted was the first x-ray image that was shown in the public.

"röntgen", very happy to see this word here ;-D

Why does the rubber duck have such an image? Included contraband? Or a subtle reference to the use of ducks in optical transforms, related to X-ray diffraction?
http://books.google.com/books?id=fye--TBu4T0C&pg=PA155&dq=optical+transform+duck&hl=en&ei=nI_XTJPYHZG2sAPV6OWMCw&sa=X&oi=book_result&ct=book-thumbnail&resnum=2&ved=0CDgQ6wEwAQ#v=onepage&q=optical%20transform%20duck&f=false

arindam It's a pigeon indeed, it refers to PigeonRank according to Marissa Mayer "with a shoutout to April Fools 2002 – PigeonRank – in the little 'g'"

Why do we have a key in Logo? Wat is the importance of key?

Well, it is a skeleton key.

A correct answer :)