TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The reducing agent is hydrazine, sodium borohydride and/or hydrogen gas. The precipitating agent is an acidic solution. The catalytic metal precursor is H2PtCl4, H2PtCl6, K2PtCl4, H2PtCl6, (NH4)2(RuCl6), (NH4)2(RuCl5H2O), H2(AuCl4), (NH4)2(AuCl4), H(Au(NO3)4)H2O and/or RuCl3. The catalyst support is Vulcan, Ketjen black, acetylene black, activated carbon powder, carbon molecular sieve, carbon nanotube, activated carbon having micropores, and/or mesoporous.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The reducing agent is formaldehyde, formic acid and/or polyol. The solvent is polyol, alcohol and/or water.    TECHNOLOGY FOCUS - POLYMERS - The cation exchange polymer is at least one of perfluorocarbon sulfonic acid cation exchange resin, sulfonated polyimide, sulfonated polyetherketone, sulfonated polystyrene and/or sulfonated polysulfone. The cation exchange polymer content is 4 - 40 parts by weight based on 100 parts by weight of the catalytic metal precursor. The cation exchange polymer content is 1 - 10 parts by weight based on 100 parts by weight of the catalyst support. The average particle size of the catalytic metal particles of the supported catalyst is 2 - 5 nm. Preferred Method: The pH of the mixture is 7 - 12. Heating the mixture involves heating the mixture to 70 - 90degreesC. The catalytic metal precursor in the catalytic metal precursor containing solution is 0.1 - 100 mg/ml. The method further involves preparing a cathode or an anode of a fuel cell using the filtered and dried precipitates. The method involves producing from a catalytic metal precursor, catalytic metal particles having an average size of 2 - 5 nm by adjusting a pH of a mixture to within a range to obtain a resultant, the mixture is of a cation exchange polymer solution and a catalytic metal precursor; heating the resultant to within a temperature range; and combining a reducing agent with the heated resultant to reduce the catalytic metal precursor to obtain the catalytic metal particles having the average size of 2 - 5 nm; and then mixing the another resultant with a catalyst support such that the catalyst support supports catalytic metal particles. EXAMPLE - Ethanol (10 ml) was added to a solution of NAFION (RTM; cation exchange polymer) solution (133 mg, 5 wt.%) was added. Then hexachloroplatinic (IV) acid aqueous solution (8.1 ml) in ethylene glycol (Pt content: 7.4 mg Pt/ml EG) was added, followed by the addition of sodium hydroxide (1M, 4.5 ml) solution until a pH of 8 had been reached. After stirring for 30 minutes, the mixture was heated to 80degreesC. A formaldehyde solution in alcohol (7 ml) was added dropwise and stirred, and then cooled to room temperature. 90 mg of Vulcan XC-72 (RTM; catalyst support) was added to the obtained mixture and homogeneously mixed by stirring. After adding 1.5 M hydrochloric acid aqueous solution (9.1 ml) as a precipitating agent, the mixture was stirred for 6 hours, then filtered and washed with deionized water. The resultant was dried in an oven at 70degreesC to obtain 40 wt.% Pt/C particles. An average particle size of the Pt/C particles was about 2.5 - 3 nm.