Capacitance step size distributions measured in cells stimulated with 20 μmol/L GTPγS after 10 to 14 days in culture (A) and after 15 to 21 days in culture (B). A clear peak between 6 and 7 fF and additional peaks at multiples of this value are seen. The moving bin technique was used with a bin size of 1.8 fF and a bin increment of 0.1 fF in (A) and with a bin size of 2 fF and a bin increment of 0.2 fF in (B). The additional peak at <4 fF in (B) reflects exocytosis of a distinct class of small vesicles.