# Measure on cryo stock
The cryo stock is the starting point for preparing the dilution series. It will likely contain a mix of culturable, viable-but-non-culturable (VBNC), and dead cells. Knowing the cell concentration helps determine how far the dilution can go before cells are virtually absent in the growth medium. We will use a 1:1 000 dilution in two sequential dilution steps: An initial 1:100 dilution followed by a additional 1:10 dilution.
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### Disaggregate cell clumps
Allow the cryo stock to thaw at room temperature.
Vortex the cryo stock 1 minute at maximum speed to disaggregate cell clumps.
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### Dilute 1:100
Transfer 101 µL of your sample to 10 mL of diluent. Vortex 10 seconds at maximum speed.
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### Dilute 1:1000
Remove 1 mL diluent from a 10 mL diluent vial for a residual volume of 9 mL.
Transfer 1 mL of the 1:100 dilution to the vial containing 9 mL of diluent. Vortex 10 seconds at maximum speed.
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### Measure on the diluted sample
Transfer the tubing kit to the 1:1 000 vial.
PressMeasure in Access to start a new measurement.
* Dilution: 1 000
* Label: E\_coli\_cryo
After completing the measurement, Access will automatically calculate the bacterial concentration in the cryo stock in the field Cells/mL × Dil.
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## Summary
Now you know the bacterial concentration of your cryo stock. \
Next step: [prepare-dilution-series](https://help.sbtinstruments.com/protocols/optimize-bioprocesses/identify-optimal-inoculum-size/prepare-dilution-series "mention").
