diff --git a/README.md b/README.md
index 71cdc2d..69425f3 100644
--- a/README.md
+++ b/README.md
@@ -79,7 +79,7 @@ To apply this library to types of one-dimensional intervals, you must provide a
   import "github.com/gaissmai/interval"
 
   type Tree[T any] struct{ ... }
-  func NewTree[T any](cmp func(a, b T) (ll, rr, lr, rl int)) Tree[T]
+  func NewTree[T any](cmp func(a, b T) (ll, rr, lr, rl int), items ...T) Tree[T]
 
   func (t Tree[T]) Insert(items ...T) Tree[T]
   func (t Tree[T]) Delete(item T) (Tree[T], bool)
diff --git a/bench_test.go b/bench_test.go
index 1d33263..fb07c5d 100644
--- a/bench_test.go
+++ b/bench_test.go
@@ -17,11 +17,9 @@ var intMap = map[int]string{
 	1_000_000: "1_000_000",
 }
 
-var tree = interval.NewTree(compareIval)
-
 func BenchmarkInsert(b *testing.B) {
 	for n := 1; n <= 1_000_000; n *= 10 {
-		tree := tree.Insert(generateIvals(n)...)
+		tree := interval.NewTree(compareIval, generateIvals(n)...)
 
 		probe := generateIvals(1)[0]
 		name := "Into" + intMap[n]
@@ -37,7 +35,7 @@ func BenchmarkInsert(b *testing.B) {
 
 func BenchmarkInsertMutable(b *testing.B) {
 	for n := 1; n <= 1_000_000; n *= 10 {
-		tree := tree.Insert(generateIvals(n)...)
+		tree := interval.NewTree(compareIval, generateIvals(n)...)
 		probe := generateIvals(1)[0]
 		name := "Into" + intMap[n]
 
@@ -55,7 +53,7 @@ func BenchmarkDelete(b *testing.B) {
 		ivals := generateIvals(n)
 		probe := ivals[rand.Intn(len(ivals))]
 
-		tree := tree.Insert(ivals...)
+		tree := interval.NewTree(compareIval, ivals...)
 		name := "DeleteFrom" + intMap[n]
 
 		b.Run(name, func(b *testing.B) {
@@ -72,7 +70,7 @@ func BenchmarkDeleteMutable(b *testing.B) {
 		ivals := generateIvals(n)
 		probe := ivals[rand.Intn(len(ivals))]
 
-		tree := tree.Insert(generateIvals(n)...)
+		tree := interval.NewTree(compareIval, generateIvals(n)...)
 		name := "DeleteFrom" + intMap[n]
 
 		b.Run(name, func(b *testing.B) {
@@ -86,7 +84,7 @@ func BenchmarkDeleteMutable(b *testing.B) {
 
 func BenchmarkClone(b *testing.B) {
 	for n := 10; n <= 10_000; n *= 10 {
-		tree := tree.Insert(generateIvals(n)...)
+		tree := interval.NewTree(compareIval, generateIvals(n)...)
 		name := intMap[n]
 
 		b.Run(name, func(b *testing.B) {
@@ -99,9 +97,9 @@ func BenchmarkClone(b *testing.B) {
 }
 
 func BenchmarkUnionImmutable(b *testing.B) {
-	this100_000 := tree.Insert(generateIvals(100_000)...)
+	this100_000 := interval.NewTree(compareIval, generateIvals(100_000)...)
 	for n := 10; n <= 100_000; n *= 10 {
-		tree := tree.Insert(generateIvals(n)...)
+		tree := interval.NewTree(compareIval, generateIvals(n)...)
 		name := "size100_000with" + intMap[n]
 
 		b.Run(name, func(b *testing.B) {
@@ -115,8 +113,8 @@ func BenchmarkUnionImmutable(b *testing.B) {
 
 func BenchmarkUnionMutable(b *testing.B) {
 	for n := 10; n <= 100_000; n *= 10 {
-		this100_000 := tree.Insert(generateIvals(100_000)...)
-		tree := tree.Insert(generateIvals(n)...)
+		this100_000 := interval.NewTree(compareIval, generateIvals(100_000)...)
+		tree := interval.NewTree(compareIval, generateIvals(n)...)
 		name := "size100_000with" + intMap[n]
 
 		b.Run(name, func(b *testing.B) {
@@ -131,7 +129,7 @@ func BenchmarkUnionMutable(b *testing.B) {
 func BenchmarkIntersects(b *testing.B) {
 	for n := 1; n <= 1_000_000; n *= 10 {
 		ivals := generateIvals(n)
-		tree := tree.Insert(ivals...)
+		tree := interval.NewTree(compareIval, ivals...)
 		probe := ivals[rand.Intn(len(ivals))]
 		name := "In" + intMap[n]
 
@@ -147,7 +145,7 @@ func BenchmarkIntersects(b *testing.B) {
 func BenchmarkFind(b *testing.B) {
 	for n := 1; n <= 1_000_000; n *= 10 {
 		ivals := generateIvals(n)
-		tree := tree.Insert(ivals...)
+		tree := interval.NewTree(compareIval, ivals...)
 		probe := ivals[rand.Intn(len(ivals))]
 		name := "In" + intMap[n]
 
@@ -162,7 +160,7 @@ func BenchmarkFind(b *testing.B) {
 
 func BenchmarkCoverLCP(b *testing.B) {
 	for n := 100; n <= 1_000_000; n *= 10 {
-		tree := tree.Insert(generateIvals(n)...)
+		tree := interval.NewTree(compareIval, generateIvals(n)...)
 		probe := generateIvals(1)[0]
 		name := "In" + intMap[n]
 
@@ -177,7 +175,7 @@ func BenchmarkCoverLCP(b *testing.B) {
 
 func BenchmarkCoverSCP(b *testing.B) {
 	for n := 100; n <= 1_000_000; n *= 10 {
-		tree := tree.Insert(generateIvals(n)...)
+		tree := interval.NewTree(compareIval, generateIvals(n)...)
 		probe := generateIvals(1)[0]
 		name := "In" + intMap[n]
 
@@ -192,7 +190,7 @@ func BenchmarkCoverSCP(b *testing.B) {
 
 func BenchmarkCoveredBy(b *testing.B) {
 	for n := 100; n <= 100_000; n *= 10 {
-		tree := tree.Insert(generateIvals(n)...)
+		tree := interval.NewTree(compareIval, generateIvals(n)...)
 		probe := generateIvals(1)[0]
 		name := "In" + intMap[n]
 
@@ -207,7 +205,7 @@ func BenchmarkCoveredBy(b *testing.B) {
 
 func BenchmarkCovers(b *testing.B) {
 	for n := 100; n <= 100_000; n *= 10 {
-		tree := tree.Insert(generateIvals(n)...)
+		tree := interval.NewTree(compareIval, generateIvals(n)...)
 		probe := generateIvals(1)[0]
 		name := "In" + intMap[n]
 
@@ -222,7 +220,7 @@ func BenchmarkCovers(b *testing.B) {
 
 func BenchmarkPrecededBy(b *testing.B) {
 	for m := 100; m <= 10_000; m *= 10 {
-		tree := tree.Insert(generateIvals(m)...)
+		tree := interval.NewTree(compareIval, generateIvals(m)...)
 		probe := generateIvals(1)[0]
 		name := "In" + intMap[m]
 
@@ -237,7 +235,7 @@ func BenchmarkPrecededBy(b *testing.B) {
 
 func BenchmarkPrecedes(b *testing.B) {
 	for m := 100; m <= 10_000; m *= 10 {
-		tree := tree.Insert(generateIvals(m)...)
+		tree := interval.NewTree(compareIval, generateIvals(m)...)
 		probe := generateIvals(1)[0]
 		name := "In" + intMap[m]
 
@@ -252,7 +250,7 @@ func BenchmarkPrecedes(b *testing.B) {
 
 func BenchmarkIntersections(b *testing.B) {
 	for n := 100; n <= 10_000; n *= 10 {
-		tree := tree.Insert(generateIvals(n)...)
+		tree := interval.NewTree(compareIval, generateIvals(n)...)
 		probe := generateIvals(1)[0]
 		name := "In" + intMap[n]
 
@@ -268,7 +266,7 @@ func BenchmarkIntersections(b *testing.B) {
 func BenchmarkMin(b *testing.B) {
 	for n := 100; n <= 1_000_000; n *= 10 {
 		ivals := generateIvals(n)
-		tree := tree.Insert(ivals...)
+		tree := interval.NewTree(compareIval, ivals...)
 		name := "In" + intMap[n]
 
 		b.Run(name, func(b *testing.B) {
@@ -283,7 +281,7 @@ func BenchmarkMin(b *testing.B) {
 func BenchmarkMax(b *testing.B) {
 	for n := 100; n <= 1_000_000; n *= 10 {
 		ivals := generateIvals(n)
-		tree := tree.Insert(ivals...)
+		tree := interval.NewTree(compareIval, ivals...)
 		name := "In" + intMap[n]
 
 		b.Run(name, func(b *testing.B) {
diff --git a/example_period_test.go b/example_period_test.go
index 85b8a29..8a3eda8 100644
--- a/example_period_test.go
+++ b/example_period_test.go
@@ -40,8 +40,7 @@ func compareIval(p, q Ival) (ll, rr, lr, rl int) {
 }
 
 func ExampleNewTree() {
-	tree1 := interval.NewTree(compareIval)
-	tree1.InsertMutable(periods...)
+	tree1 := interval.NewTree(compareIval, periods...)
 
 	tree1.Fprint(os.Stdout)
 	// Output:
@@ -53,7 +52,7 @@ func ExampleNewTree() {
 }
 
 func ExampleTree_Max() {
-	tree1 := tree.Insert(periods...)
+	tree1 := interval.NewTree(compareIval, periods...)
 	tree1.Fprint(os.Stdout)
 
 	fmt.Println("\nInterval with max value in tree:")
@@ -71,7 +70,7 @@ func ExampleTree_Max() {
 }
 
 func ExampleTree_Covers() {
-	tree1 := tree.Insert(periods...)
+	tree1 := interval.NewTree(compareIval, periods...)
 	tree1.Fprint(os.Stdout)
 
 	item := Ival{3, 4}
@@ -94,7 +93,7 @@ func ExampleTree_Covers() {
 }
 
 func ExampleTree_CoveredBy() {
-	tree1 := tree.Insert(periods...)
+	tree1 := interval.NewTree(compareIval, periods...)
 	tree1.Fprint(os.Stdout)
 
 	item := Ival{3, 10}
@@ -117,7 +116,7 @@ func ExampleTree_CoveredBy() {
 }
 
 func ExampleTree_Precedes_period() {
-	tree1 := tree.Insert(periods...)
+	tree1 := interval.NewTree(compareIval, periods...)
 	tree1.Fprint(os.Stdout)
 
 	item := Ival{6, 6}
@@ -139,7 +138,7 @@ func ExampleTree_Precedes_period() {
 }
 
 func ExampleTree_Visit() {
-	tree1 := tree.Insert(periods...)
+	tree1 := interval.NewTree(compareIval, periods...)
 	fmt.Println("parent/child printing")
 	tree1.Fprint(os.Stdout)
 
diff --git a/example_time_test.go b/example_time_test.go
index 02e2d91..809cb17 100644
--- a/example_time_test.go
+++ b/example_time_test.go
@@ -47,8 +47,6 @@ func compareTval(p, q Tval) (ll, rr, lr, rl int) {
 		cmpTime(p.death, q.birth)
 }
 
-var timeTree = interval.NewTree(compareTval)
-
 // example data
 var physicists = []Tval{
 	mkTval(1473, 1543, "Kopernikus"),
@@ -82,11 +80,11 @@ var physicists = []Tval{
 }
 
 func ExampleTree_Precedes_time() {
-	tree := timeTree.Insert(physicists...)
+	tree := interval.NewTree(compareTval, physicists...)
 	tree.Fprint(os.Stdout)
 
 	precedes := tree.Precedes(mkTval(1643, 1727, "Newton"))
-	tree = timeTree.Insert(precedes...)
+	tree = interval.NewTree(compareTval, precedes...)
 
 	fmt.Println("\nPrecedes Newton:")
 	tree.Fprint(os.Stdout)
@@ -131,11 +129,11 @@ func ExampleTree_Precedes_time() {
 }
 
 func ExampleTree_PrecededBy_time() {
-	tree := timeTree.Insert(physicists...)
+	tree := interval.NewTree(compareTval, physicists...)
 	tree.Fprint(os.Stdout)
 
 	precededBy := tree.PrecededBy(mkTval(1643, 1727, "Newton"))
-	tree = timeTree.Insert(precededBy...)
+	tree = interval.NewTree(compareTval, precededBy...)
 
 	fmt.Println("\nPrecededBy Newton:")
 	tree.Fprint(os.Stdout)
diff --git a/treap.go b/treap.go
index 27d38f4..8da20c2 100644
--- a/treap.go
+++ b/treap.go
@@ -32,7 +32,7 @@ type Tree[T any] struct {
 	cmp  func(T, T) (ll, rr, lr, rl int)
 }
 
-// NewTree initializes the interval tree with the interval comparison function for type T.
+// NewTree initializes the interval tree with the compare function and items from type T.
 //
 //   cmp(a, b T) (ll, rr, lr, rl int)
 //
@@ -43,9 +43,15 @@ type Tree[T any] struct {
 //  lr: left  point interval a compared with right point interval b (-1, 0, +1)
 //  rl: right point interval a compared with left  point interval b (-1, 0, +1)
 //
-func NewTree[T any](cmp func(a, b T) (ll, rr, lr, rl int)) Tree[T] {
+func NewTree[T any](cmp func(a, b T) (ll, rr, lr, rl int), items ...T) Tree[T] {
 	var t Tree[T]
 	t.cmp = cmp
+
+	// mutable insert
+	for i := range items {
+		t.root = t.root.insert(t.makeNode(items[i]), false, &t)
+	}
+
 	return t
 }
 
diff --git a/treap_test.go b/treap_test.go
index 4c78274..13efe76 100644
--- a/treap_test.go
+++ b/treap_test.go
@@ -173,7 +173,7 @@ func TestTreeWithDups(t *testing.T) {
 		{3, 13},
 	}
 
-	tree1 := tree.Insert(is...)
+	tree1 := interval.NewTree(compareIval, is...)
 	if size, _, _, _ := tree1.Statistics(); size != 5 {
 		t.Errorf("Size() = %v, want 5", size)
 	}
@@ -192,7 +192,7 @@ func TestTreeWithDups(t *testing.T) {
 
 func TestImmutable(t *testing.T) {
 	t.Parallel()
-	tree1 := tree.Insert(ps...)
+	tree1 := interval.NewTree(compareIval, ps...)
 
 	if _, ok := tree1.Delete(tree1.Min()); !ok {
 		t.Fatal("Delete, could not delete min item")
@@ -210,7 +210,7 @@ func TestImmutable(t *testing.T) {
 }
 
 func TestMutable(t *testing.T) {
-	tree1 := tree.Insert(ps...)
+	tree1 := interval.NewTree(compareIval, ps...)
 	clone := tree1.Clone()
 
 	if !equalStatistics(tree1, clone) {
@@ -233,7 +233,7 @@ func TestMutable(t *testing.T) {
 	}
 
 	// reset
-	tree1 = tree.Insert(ps...)
+	tree1 = interval.NewTree(compareIval, ps...)
 	clone = tree1.Clone()
 
 	if !equalStatistics(tree1, clone) {
@@ -252,7 +252,7 @@ func TestFind(t *testing.T) {
 	t.Parallel()
 
 	ivals := generateIvals(100_00)
-	tree1 := tree.Insert(ivals...)
+	tree1 := interval.NewTree(compareIval, ivals...)
 
 	for _, ival := range ivals {
 		item, ok := tree1.Find(ival)
@@ -271,7 +271,7 @@ func TestLookup(t *testing.T) {
 
 	for i := 0; i < 100; i++ {
 		// bring some variance into the Treap due to the prio randomness
-		tree1 := tree.Insert(ps...)
+		tree1 := interval.NewTree(compareIval, ps...)
 
 		//     	 ▼
 		//     	 ├─ 0...6
@@ -348,7 +348,7 @@ func TestLookup(t *testing.T) {
 func TestCoveredBy(t *testing.T) {
 	t.Parallel()
 
-	tree1 := tree.Insert(ps...)
+	tree1 := interval.NewTree(compareIval, ps...)
 	var want []Ival
 
 	//     	 ▼
@@ -394,7 +394,7 @@ func TestCoveredBy(t *testing.T) {
 func TestCovers(t *testing.T) {
 	t.Parallel()
 
-	tree1 := tree.Insert(ps...)
+	tree1 := interval.NewTree(compareIval, ps...)
 	var want []Ival
 
 	//     	 ▼
@@ -440,7 +440,7 @@ func TestCovers(t *testing.T) {
 func TestIntersects(t *testing.T) {
 	t.Parallel()
 
-	tree1 := tree.Insert(ps...)
+	tree1 := interval.NewTree(compareIval, ps...)
 
 	//     	 ▼
 	//     	 ├─ 0...6
@@ -491,7 +491,7 @@ func TestIntersects(t *testing.T) {
 func TestIntersections(t *testing.T) {
 	t.Parallel()
 
-	tree1 := tree.Insert(ps...)
+	tree1 := interval.NewTree(compareIval, ps...)
 	var want []Ival
 
 	//     	 ▼
@@ -537,7 +537,7 @@ func TestIntersections(t *testing.T) {
 func TestPrecedes(t *testing.T) {
 	t.Parallel()
 
-	tree1 := tree.Insert(ps...)
+	tree1 := interval.NewTree(compareIval, ps...)
 	var want []Ival
 
 	//     	 ▼
@@ -583,7 +583,7 @@ func TestPrecedes(t *testing.T) {
 func TestPrecededBy(t *testing.T) {
 	t.Parallel()
 
-	tree1 := tree.Insert(ps...)
+	tree1 := interval.NewTree(compareIval, ps...)
 	var want []Ival
 
 	//     	 ▼
@@ -628,7 +628,7 @@ func TestPrecededBy(t *testing.T) {
 
 func TestVisit(t *testing.T) {
 	t.Parallel()
-	tree1 := tree.Insert(ps...)
+	tree1 := interval.NewTree(compareIval, ps...)
 
 	var collect []Ival
 	want := 4
@@ -663,7 +663,7 @@ func TestVisit(t *testing.T) {
 
 func TestMinMax(t *testing.T) {
 	t.Parallel()
-	tree1 := tree.Insert(ps...)
+	tree1 := interval.NewTree(compareIval, ps...)
 	want := Ival{0, 6}
 	if tree1.Min() != want {
 		t.Fatalf("Min(), want: %v, got: %v", want, tree1.Min())
@@ -677,7 +677,7 @@ func TestMinMax(t *testing.T) {
 
 func TestUnion(t *testing.T) {
 	t.Parallel()
-	tree1 := tree.Insert()
+	tree1 := interval.NewTree(compareIval)
 
 	for i := range ps {
 		b := tree1.Insert(ps[i])
@@ -760,7 +760,7 @@ func TestStatistics(t *testing.T) {
 	for n := 10_000; n <= 1_000_000; n *= 10 {
 		count := strconv.Itoa(n)
 		t.Run(count, func(t *testing.T) {
-			tree1 := tree.Insert(generateIvals(n)...)
+			tree1 := interval.NewTree(compareIval, generateIvals(n)...)
 
 			size, _, averageDepth, deviation := tree1.Statistics()
 			if size != n {
@@ -784,7 +784,7 @@ func TestStatistics(t *testing.T) {
 
 func TestPrintBST(t *testing.T) {
 	t.Parallel()
-	tree1 := tree.Insert(ps...)
+	tree1 := interval.NewTree(compareIval, ps...)
 
 	w := new(strings.Builder)
 	_ = tree1.FprintBST(w)
@@ -798,7 +798,7 @@ func TestPrintBST(t *testing.T) {
 
 func TestMatch(t *testing.T) {
 	t.Parallel()
-	tree1 := tree.Insert(generateIvals(100_000)...)
+	tree1 := interval.NewTree(compareIval, generateIvals(100_000)...)
 
 	n := 100
 	for i := 0; i < n; i++ {
@@ -849,7 +849,7 @@ func TestMatch(t *testing.T) {
 
 func TestMissing(t *testing.T) {
 	t.Parallel()
-	tree1 := tree.Insert(generateIvals(100_000)...)
+	tree1 := interval.NewTree(compareIval, generateIvals(100_000)...)
 
 	n := 100
 	for i := 0; i < n; i++ {