medium: 10%FBS in 1x AA, warm up for 1 hour before use
pass 1 to 4 in petri dish when crowded (twice a week):
vacuum out old medium, add 4mL trypsin-EDTA, incubate 3 minutes until cells float to top, add 4mL medium.
centrifuge 5 minutes, vacuum out supernatant, add 4mL medium to cells, mix thoroughly.
Add 1mL to each of 4 new petri dishes.
add medium to make total of 5mL solution if transferring to small petri dishes, 25mL if transferring to large petri dishes.