diff --git a/README.md b/README.md
index 7e899c6..e2e6e93 100644
--- a/README.md
+++ b/README.md
@@ -34,4 +34,35 @@ In the **setup** function, we also need to set up the **pinMode** for the added
 to have a **LOW** or **HIGH** digital value in the corresponding circuit.
 
 ## step3 function
-hh 
+
+![step3](25.png)
+
+In the lines 200 to 206 from the **pool_kit_modified.ino** file, we modified this function by adding the next 
+instructions:
+
+**DO.send_read_cmd();**
+**EC.send_read_cmd();**
+
+These pair of instructions are commands defined in the libraries from Atlas Scientific imported to the Arduino IDE.
+In this part, as we are addidng different sensors and circuits to our kit, we use these instructions to extract the 
+readings of the measurements in the sensors, so that we can process those signals and show in the _Serial Monitor_ 
+the corresponding numeric data. 
+
+In this case for this function, we have removed the command for the pH variable since this parameters was not going 
+to be used for data analysis.
+
+## Printing in the Serial Monitor
+
+![print1](26.png)
+
+![print2](27.png)
+
+The last changes in the original source code were made in the **step4** function. 
+
+All the data showed in the Serial Monitor consists on rows, and each of them has 4 numeric data in the next 
+order: temperature, dissolved oxygen, ORP and conductivity. The changes made for this **step4** function allow 
+the user to print these 4 data one next to the other and separated by commas. This printing format was not available
+in the original source code downloaded from the Atlas Scientific website, but the changes are very useful, since the 
+format now we have for the results in the Serial Monitor let us only copy the results printed into a .CSV file. 
+And as we mentioned at the beginning, the .CSV file format makes it easier to import the data into a Python 
+environment.