I have in a MySQL database with the column type being DateTime the following time:

Timestamp:
9:34:09
9:34:23
9:34:45
9:34:50
9:35:09
9:36:17

But a DataGridView in C# only shows me
9:34
9:34
9:34
9:34
9:35
9:36

Why?

Did you check the format of your string?
Format for DateTime strings can be found here.

try to use Column.DefaultCellStyle.Format property or set it via designer....

Solved it with this code:

 try 
            {
                dataGridView1.Columns["Time_Stamp"].DefaultCellStyle.Format = "yyyy-MM-dd hh:mm:ss";

            }
            catch (Exception x)
            {

                MessageBox.Show(x.Message);
            }