.grid {
	background-color: #efefef;
	transform-origin: top center;
	transition: transform 0.5s;
}

.grid-item {
	background-color: #ffffff;
	-webkit-transition: width 0.25s, height 0.25s, transform 0.5s;
	-moz-transition: width 0.25s, height 0.25s, transform 0.5s;
	-o-transition: width 0.25s, height 0.25s, transform 0.5s;
	transition: width 0.25s, height 0.25s, transform 0.5s;
}

.grid-item:active, .grid-item.moving {
	z-index: 2;
	-webkit-transition: none;
	-moz-transition: none;
	-o-transition: none;
	transition: none;
}

.grid-placeholder {
	background-color: rgba(0, 0, 0, 0.3);
}
.grid {
	background-color: #efefef;
	transform-origin: top center;
	transition: transform 0.5s;
}

.grid-item {
	background-color: #ffffff;
	-webkit-transition: width 0.25s, height 0.25s, transform 0.5s;
	-moz-transition: width 0.25s, height 0.25s, transform 0.5s;
	-o-transition: width 0.25s, height 0.25s, transform 0.5s;
	transition: width 0.25s, height 0.25s, transform 0.5s;
	overflow: hidden;
}

.grid-item:active, .grid-item.moving {
	z-index: 2;
	-webkit-transition: none;
	-moz-transition: none;
	-o-transition: none;
	transition: none;
}

.grid-placeholder {
	background-color: rgba(0, 0, 0, 0.3);
}
Add overflow: hidden; to grid item css
Add overflow: hidden; to grid item css
