I've asked some of our regular viewers to list their top five videos from the Periodic Table of Videos (we've posted more than 200).
I thought it might be fun - and it's always useful to know what people do and don't like.
The first contribution comes from regular viewer Sarah, known on YouTube as CoolMinty and on Twitter as @SarahScientist
Here are her five choices in "no particular order".
1. CHRISTMAS SPECIAL 2008
Sarah says: "The Christmas Special with the Chemical Sisters is a fun video for my favourite season. I watched this many times when it was first made and thought it a great idea making an instrument out of test tubes. It's nice to see which elements people like and why. I expected Steve Liddle's favourite element to be Uranium and am still intrigued to know what it really is?"
2. EXPLODING CAKE
Sarah says: "It has cake and explosions, need I say more? Lovely way to celebrate PTOV's first birthday."
Sarah says: "My favourite element, even if some people think it is evil. I learned a bit more about it too."
4. ETHIOPIAN PERIODIC TABLE
Sarah says: "This shows how scientists work when going on trips/conferences/ meetings etc. It is a fine example of science communication, encouraging kids and shows how PTOV's can be used in schools."
5. MERCURY BELL
Sarah says: "Fascinating to see two (eccentric) scientists chatting about chemistry and this shows how innovative science can be."
Thanks again to Sarah.
I'll be posting a few more top fives over the next few weeks or months (including my own, although is that a bit like choosing your favourite child!!!?).
Your own contributions are also welcome.