Plenty of Room at the BottomRichard P. Feynman(Dated: Dec. 1959)This is the transcript of a talk presented by Richard P. Feynman to the American Physical Societyin Pasadena on December 1959, which explores the immense possibilities afforded by miniaturization.I imagine experimental physicists must often look withenvy at men like Kamerlingh Onnes, who discovered afield like low temperature, which seems to be bottomlessand in which one can go down and down. Such a manis then a leader and has some temporary monopoly ina scientific adventure. Percy Bridgman, in designing away to obtain higher pressures, opened up another newfield and was able to move into it and to lead us all along.The development of ever higher vacuum was a continuingdevelopment of the same kind.I would like to describe a field, in which little has beendone, but in which an enormous amount can be done inprinciple. This field is not quite the same as the othersin that it will not tell us much of fundamental physics (inthe sense of, “What are the strange particles?”) but it ismore like solid-state physics in the sense that it might tellus much of great interest about the strange phenomenathat occur in complex situations. Furthermore, a pointthat is most important is that it would have an enormousnumber of technical applications.What I want to talk about is the problem of manipu-lating and controlling things on a small scale.As soon as I mention this, people tell me about minia-turization, and how far it has progressed today. They tellme about electric motors that are the size of the nail onyour small finger. And there is a device on the market,they tell me, by which you can write the Lord’s Prayeron the head of a pin. But that’s nothing; that’s the mostprimitive, halting step in the direction I intend to dis-cuss. It is a staggeringly small world that is below. Inthe year 2000, when they look back at this age, they willwonder why it was not until the year 1960 that anybodybegan seriously to move in this direction.Why cannot we write the entire 24 volumes of the En-cyclopedia Brittanica on the head of a pin?Let’s see what would be involved. The head of a pin isa sixteenth of an inch across. If you magnify it by 25,000diameters, the area of the head of the pin is then equal tothe area of all the pages of the Encyclopaedia Brittanica.Therefore, all it is necessary to do is to reduce in sizeall the writing in the Encyclopaedia by 25,000 times. Isthat possible? The resolving power of the eye is about1/120 of an inch—that is roughly the diameter of one ofthe little dots on the fine half-tone reproductions in theEncyclopaedia. This, when you demagnify it by 25,000times, is still 80 angstroms in diameter—32 atoms across,in an ordinary metal. In other words, one of those dotsstill would contain in its area 1,000 atoms. So, each dotcan easily be adjusted in size as required by the photo-engraving, and there is no question that there is enoughroom on the head of a pin to put all of the EncyclopaediaBrittanica.Furthermore, it can be read if it is so written. Let’simagine that it is written in raised letters of metal; thatis, where the black is in the Encyclopedia, we have raisedletters of metal that are actually 1/25,000 of their ordi-nary size. How would we read it?If we had something written in such a way, we couldread it using techniques in common use today. (They willundoubtedly find a better way when we do actually haveit written, but to make my point conservatively I shalljust take techniques we know today.) We would pressthe metal into a plastic material and make a mold of it,then peel the plastic off very carefully, evaporate silicainto the plastic to get a very thin film, then shadow it byevaporating gold at an angle against the silica so that allthe little letters will appear clearly, dissolve the plasticaway from the silica film, and then look through it withan electron microscope!There is no question that if the thing were reduced by25,000 times in the form of raised letters on the pin, itwould be easy for us to read it today. Furthermore; thereis no question that we would find it easy to make copiesof the master; we would just need to press the same metalplate again into plastic and we would have another copy.How do we write small?The next question is: How do we write it? We haveno standard technique to do this now. But let me arguethat it is not as difficult as it first appears to be. Wecan reverse the lenses of the electron microscope in or-der to demagnify as well as magnify. A source of ions,sent through the microscope lenses in reverse, could befocused to a very small spot. We could write with thatspot like we write in a TV cathode ray oscilloscope, bygoing across in lines, and having an adjustment whichdetermines the amount of material which is going to bedeposited as we scan in lines.This method might be very slow because of spacecharge limitations. There will be more rapid methods.We could first make, perhaps by some photo process, ascreen which has holes in it in the form of the letters.Then we would strike an arc behind the holes and drawmetallic ions through the holes; then we could again useour system of lenses and make a small image in the formof ions, which would deposit the metal on the pin.A simpler way might be this (though I am not sure it2would work): We take light and, through an optical mi-croscope running backwards, we focus it onto a very smallphotoelectric screen. Then electrons come away from thescreen where the light is shining. These electrons are fo-cused down in size by the electron microscope lenses toimpinge directly upon the surface of the metal. Will sucha beam etch away the metal if it is run long enough? Idon’t know. If it doesn’t work for a metal surface, itmust be possible to find some surface with which to coatthe original pin so that, where the electrons bombard, achange is made which we could recognize later.There is no intensity problem in these devices—notwhat you are used to in magnification, where you haveto take a few electrons and spread them over a bigger andbigger screen; it is just the opposite. The light which weget from a page is concentrated onto a very small areaso it is very intense. The few electrons which come fromthe photoelectric screen are demagnified down to a verytiny area so that, again, they are very intense. I don’tknow why this hasn’t been done yet!That’s the Encyclopaedia Brittanica on the head of apin, but let’s