How to make picturebox transparent?

Try using an ImageList

ImageList imgList = new ImageList;

imgList.TransparentColor = Color.White;

Load the image like this:

picturebox.Image = imgList.Images[img_index];

GameBoard is control of type DataGridView; The image should be type of PNG with transparent alpha channel background;

        Image test = Properties.Resources.checker_black;
        PictureBox b = new PictureBox();
        b.Parent = GameBoard;
        b.Image = test;
        b.Width = test.Width*2;
        b.Height = test.Height*2;
        b.Location = new Point(0, 90);
        b.BackColor = Color.Transparent;
        b.BringToFront();

One way to do this is by changing the parent of the overlapping picture box to the PictureBox over which it is lapping. Since the Visual Studio designer doesn't allow you to add a PictureBox to a PictureBox, this will have to be done in your code (Form1.cs) and within the Intializing function:

public Form1()
{
    InitializeComponent();
    pictureBox7.Controls.Add(pictureBox8);
    pictureBox8.Location = new Point(0, 0);
    pictureBox8.BackColor = Color.Transparent;
}

Just change the picture box names to what ever you need. This should return: