The following protocol is for 12-well plate
  * **Preparation**
     * Plate 12-well plate with cells (85-95% confluent on the day of infection)
     
  * **Experiment**
     - Prewarm media, in 37<sup>o</sup>C water bath.
     - Prepare 11 different concentrations of virus by diluting with media.
     - Carefully remove media from 12-well plate.
     - Add 250uL of each dilution to the 11 wells. Add only media to the 12th well as a control. Swirl the plate a little to make sure the entire surface of the well is covered evenly with liquid. 
     - Incubate at room temperature for 30 minutes, swirl every ~4mins.
     - During incubation, prepare agarose.
        * Make 5% low-melt agarose in PBS. 
        * Dilute it with warm media to 1%agarose.
        * Add warm MgCl<sub>2</sub> to 40 mM final concentration.
           * (The previous steps should be carried out in the shortest amount of time possible and with warm solutions to prevent agarose from solidifying)
        * Pipette up and down to mix thoroughly.
        * Keep it in 42<sup>o</sup>C water bath.
     - When 30 mins incubation period is over, remove virus.
     - Slowly add 1mL agarose/media/MgCl<sub>2</sub> solutions to each well to form a uniform layer.
     - Leave at room temperature for agarose to solidify.
     - Add 1mL media on top of the agarose to each well.
     - Keep it in 35<sup>o</sup>C incubator.

  * **Results**
     * Observe after 1 to 2 days.
     * Observe plaques (empty spots where cells are detached) by looking at the bottom of the well. 
     * Count the no. of plaques at concentrations where individual plaques could be observed.
     * With the concentration known, PFU/mL of the original stock can be calculated.