Get Text From DataGridView Selected Cells?

I have a DataGridView with cells from a database file that contains data. Basically, I want to get the text from the selected cells in the DataGridView and display it in a textbox at the click of the button. The code for the button click event is:

Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim SelectedThings As String = DataGridView1.SelectedCells.ToString
TextBox1.Text = SelectedThings
End Sub

However in TextBox1 I get:

System.Windows.Forms.DataGridViewSelectedCellCollection

I'm thinking it isn't as simple as it seems. I'm a C developer just learning VB.NET.