 Alright, now let's try and estimate something about electronics. Inside a phone you might have 64GB of memory, how big is the circuit that can hold one of those bits of memory? Okay, so we've already said that we've got our phone, and inside that phone there's going to be a chip. So I have seen teardowns of phones, and I could guesstimate a little bit how big those chips are. So a chip is something like a 2cm square, and then they're pretty thin, maybe 2mm. That's a fairly small object to hold 64GB of memory. Now a gigabit is a billion, so 64GB is 6.4 by 10 to the 10 bits, all there abouts. So if I want to work out the volume for a single bit, it's the volume of this whole object here, this whole chip, divided by the number of bits. Now again I don't want to mix millimetres and centimetres, I want to convert it all into one unit. Rather than choosing metres for each and therefore going to cubic metres, I think I'll do the simpler thing and just convert it into centimetres. We end up with about 10-11 cubic centimetres for a single bit. Now remember that the volume scales as the length cubed, and so if I'm looking for the sort of size of a cube that would have this volume, I'd have to take the cubic root. So that number is about 2 by 10 to the minus 4. The cube root of a centimetre cubed is just a centimetre, so the unit is a centimetre, which is 2 microns, which is roughly the size of a single bit. So once again none of those estimates were accurate, but they're in the right ballpark, and that's a really important thing to be able to do yourself. And what does it take? It takes the ability to do that kind of scaling argument, because that lets you really map something you do know to something you don't know, and apart from that all it really takes is a little bit of confidence, a little bit of practice. So have a go yourself at a couple of unfamiliar examples and see how you go.