In　situ　growth　of　copper　nanocrystals　from　carbon/copper　microspheres　was　observed　in　a　well-controlled　annealing　or　an　electron　beam　irradiation　process.　Carbonaceous　microspheres　containing　copper　species　with　a　smooth　appearance　were　yielded　by　a　hydrothermal　synthesis　using　copper　nitrate　and　ascorbic　acid　as　reactants.　When　annealing　the　carbonaceous　microspheres　under　inert　atmosphere,　copper　nanoparticles　were　formed　on　carbon　microspheres　and　the　copper　particle　sizes　can　be　increased　to　a　range　of　50-500　nm　by　altering　the　heating　temperature.　Similarly,　in　situ　formation　of　copper　nanocrystals　from　these　carbonaceous　microspheres　was　observed　on　the　hydrothermal　product　carbonaceous　microspheres　with　electron　beam　irradiation　in　a　vacuum　transmission　electron　microscopy　chamber.　The　carbon/copper　composite　microspheres　obtained　through　annealing　were　used　to　modify　a　glassy　carbon　electrode　and　tested　as　an　electrochemical　glucose　sensor.　(C)　2013　Elsevier　Ltd.　All　rights　reserved.