Reagents Procedures StartingfromaKryotube:Prewarmthemediumat37°Candfilltwocultureflasks(25mlfor150cm2,5mlfor25cm2).Rapidlythawthecells(at37°C)anddistributethemintwoconcentrationsintheflasks.Changethemediumafter12hrsoroncethecellshaveattached. SplittingCells:Aspiratethemediumfromtheflask.WashthecellscarefullywithPBStoremoveresidualmedium.Add1-2mlofTrypsinSolution(equilibratedatRT)totheflask(150cm2)andincubateat37°Cuntilcellshavedetached(1-2minutes).Prepareanewflaskwithfreshmedium.Blocktrypsinizationbyaddingafewmlofmedium.Takeafractionofthecellsolutionandinocculatethenewflask.Typically,whensplittingconfluentHEK293cellsina1:10ratio,confluencyisreachedagainafter2-3days.