EXPH shares COULD trade at .000001 (negative 6 digits) actually. Perfectly legal...as long as there is a pink sheet market maker or even more important, a broker member, willing to deal with it and the minimum order was 5000 shares or more. That price simply cannot be DISPLAYED. Nothing below .0001 is displayed as a quote on the pinks but trades at five digits and six digits DO occur making you incorrect on both counts. Expo Holdings, Inc. may get the chance to find this out soon since they have declared a "reverse split" as nothing that is to be considered". All IMHO.
(b) No member shall display, rank, or accept a bid or offer, an order, or an indication of interest in any OTC Equity Security priced in an increment smaller than $0.0001 if that bid or offer, order or indication of interest is priced less than $1.00 per share except, where an order or indication of interest is priced less than $0.0001, a member may rank or accept (but not display) such order or indication of interest in an increment of $0.000001 or greater.