diff --git a/StringTools/StringTools/StringTools.cpp b/StringTools/StringTools/StringTools.cpp
index 728506a..7e26c5c 100644
--- a/StringTools/StringTools/StringTools.cpp
+++ b/StringTools/StringTools/StringTools.cpp
@@ -59,4 +59,40 @@ std::string StringTools::Replace(const std::string& str, const std::string& find
     ss << subst;
 
     return Replace(str, find, ss.str());
-}
\ No newline at end of file
+}
+
+std::string StringTools::Lower(const std::string& str)
+{
+    std::stringstream ss;
+
+    for (std::size_t i = 0; i < str.size(); i++)
+    {
+        const char c = str[i];
+
+        // Quick-accept: regular letters
+        if ((c >= 'A') && (c <= 'Z'))
+            ss << (char)(c + 32);
+
+        // Damned umlautes:
+        else if (c == 'Ä') ss << 'ä';
+        else if (c == 'Á') ss << 'á';
+        else if (c == 'À') ss << 'à';
+        else if (c == 'Â') ss << 'â';
+        else if (c == 'É') ss << 'é';
+        else if (c == 'È') ss << 'è';
+        else if (c == 'Ê') ss << 'ê';
+        else if (c == 'Ü') ss << 'ü';
+        else if (c == 'Ú') ss << 'ú';
+        else if (c == 'Ù') ss << 'ù';
+        else if (c == 'Û') ss << 'û';
+        else if (c == 'Ö') ss << 'ö';
+        else if (c == 'Ó') ss << 'ó';
+        else if (c == 'Ò') ss << 'ò';
+        else if (c == 'Ô') ss << 'ô';
+
+        // Else: keep the character as is
+        else ss << c;
+    }
+
+    return ss.str();
+}
diff --git a/StringTools/StringTools/StringTools.h b/StringTools/StringTools/StringTools.h
index 730fa3e..39e512f 100644
--- a/StringTools/StringTools/StringTools.h
+++ b/StringTools/StringTools/StringTools.h
@@ -17,6 +17,9 @@ public:
 	//! Will replace every occurence of `find` in `str` by `subst`.
 	static std::string Replace(const std::string& str, const std::string& find, const char subst);
 
+	//! Will make a string all-lowercase. Only works with latin and german umlautes, plus some extras.
+	static std::string Lower(const std::string& str);
+
 private:
 	// No instanciation! >:(
 	StringTools();
diff --git a/StringTools/Test/Lower.cpp b/StringTools/Test/Lower.cpp
new file mode 100644
index 0000000..c45af68
--- /dev/null
+++ b/StringTools/Test/Lower.cpp
@@ -0,0 +1,200 @@
+#include "CppUnitTest.h"
+#include "../StringTools/StringTools.h"
+
+using namespace Microsoft::VisualStudio::CppUnitTestFramework;
+
+namespace _StringTools
+{
+	TEST_CLASS(_Lower)
+	{
+	public:
+
+		// Tests that lowering an empty string returns an empty string
+		TEST_METHOD(EmptyString)
+		{
+			// Setup
+			const std::string in = "";
+
+			// Exercise
+			const std::string out = StringTools::Lower(in);
+
+			// Verify
+			Assert::AreEqual("", out.c_str());
+			return;
+		}
+
+		// Tests that lowering a string without any letters returns an itself
+		TEST_METHOD(Symbols)
+		{
+			// Setup
+			const std::string in = "66! _-\n*";
+
+			// Exercise
+			const std::string out = StringTools::Lower(in);
+
+			// Verify
+			Assert::AreEqual("66! _-\n*", out.c_str());
+			return;
+		}
+
+		// Tests that lowering a string of lowercase letters returns itself
+		TEST_METHOD(AlreadyLowered)
+		{
+			// Setup
+			const std::string in = "ughareyouserious";
+
+			// Exercise
+			const std::string out = StringTools::Lower(in);
+
+			// Verify
+			Assert::AreEqual("ughareyouserious", out.c_str());
+			return;
+		}
+
+		// Tests that lowering a string of uppercase letters returns the lowercase version
+		TEST_METHOD(Uppercase)
+		{
+			// Setup
+			const std::string in = "UGHAREYOUSERIOUS";
+
+			// Exercise
+			const std::string out = StringTools::Lower(in);
+
+			// Verify
+			Assert::AreEqual("ughareyouserious", out.c_str());
+			return;
+		}
+
+		// Tests that lowering a string of uppercase, lowercase letters and symbols returns the lowercase version
+		TEST_METHOD(Mixed)
+		{
+			// Setup
+			const std::string in = "Ugh, Are You Serious?! DON'T DO THAT!!!";
+
+			// Exercise
+			const std::string out = StringTools::Lower(in);
+
+			// Verify
+			Assert::AreEqual("ugh, are you serious?! don't do that!!!", out.c_str());
+			return;
+		}
+
+		// Tests that lowering already lowered umlautes returns itself
+		TEST_METHOD(Umlautes_already_lower_a)
+		{
+			// Setup
+			const std::string in = "äáàâ";
+
+			// Exercise
+			const std::string out = StringTools::Lower(in);
+
+			// Verify
+			Assert::AreEqual("äáàâ", out.c_str());
+		}
+
+		// Tests that lowering uppercase umlautes returns the lowered umlautes
+		TEST_METHOD(Umlautes_upper_a)
+		{
+			// Setup
+			const std::string in = "ÄÁÀÂ";
+
+			// Exercise
+			const std::string out = StringTools::Lower(in);
+
+			// Verify
+			Assert::AreEqual("äáàâ", out.c_str());
+		}
+
+		// Tests that lowering already lowered umlautes returns itself
+		TEST_METHOD(Umlautes_already_lower_e)
+		{
+			// Setup
+			const std::string in = "éèê";
+
+			// Exercise
+			const std::string out = StringTools::Lower(in);
+
+			// Verify
+			Assert::AreEqual("éèê", out.c_str());
+		}
+
+		// Tests that lowering uppercase umlautes returns the lowered umlautes
+		TEST_METHOD(Umlautes_upper_e)
+		{
+			// Setup
+			const std::string in = "ÉÈÊ";
+
+			// Exercise
+			const std::string out = StringTools::Lower(in);
+
+			// Verify
+			Assert::AreEqual("éèê", out.c_str());
+		}
+
+		// Tests that lowering already lowered umlautes returns itself
+		TEST_METHOD(Umlautes_already_lower_u)
+		{
+			// Setup
+			const std::string in = "üúùû";
+
+			// Exercise
+			const std::string out = StringTools::Lower(in);
+
+			// Verify
+			Assert::AreEqual("üúùû", out.c_str());
+		}
+
+		// Tests that lowering uppercase umlautes returns the lowered umlautes
+		TEST_METHOD(Umlautes_upper_u)
+		{
+			// Setup
+			const std::string in = "ÜÚÙÛ";
+
+			// Exercise
+			const std::string out = StringTools::Lower(in);
+
+			// Verify
+			Assert::AreEqual("üúùû", out.c_str());
+		}
+
+		// Tests that lowering already lowered umlautes returns itself
+		TEST_METHOD(Umlautes_already_lower_o)
+		{
+			// Setup
+			const std::string in = "öóòô";
+
+			// Exercise
+			const std::string out = StringTools::Lower(in);
+
+			// Verify
+			Assert::AreEqual("öóòô", out.c_str());
+		}
+
+		// Tests that lowering uppercase umlautes returns the lowered umlautes
+		TEST_METHOD(Umlautes_upper_o)
+		{
+			// Setup
+			const std::string in = "ÖÓÒÔ";
+
+			// Exercise
+			const std::string out = StringTools::Lower(in);
+
+			// Verify
+			Assert::AreEqual("öóòô", out.c_str());
+		}
+
+		// Tests that lowering a string of uppercase, lowercase letters and symbols returns the lowercase version, even with umlauts
+		TEST_METHOD(Mixed_with_umlautes)
+		{
+			// Setup
+			const std::string in = "Ügh, Àrä Yóü Seriöûs?! DÓN'T DÒ THÄT!!!";
+
+			// Exercise
+			const std::string out = StringTools::Lower(in);
+
+			// Verify
+			Assert::AreEqual("ügh, àrä yóü seriöûs?! dón't dò thät!!!", out.c_str());
+			return;
+		}
+	};
+}
diff --git a/StringTools/Test/Test.vcxproj b/StringTools/Test/Test.vcxproj
index 51fba2c..59e804a 100644
--- a/StringTools/Test/Test.vcxproj
+++ b/StringTools/Test/Test.vcxproj
@@ -162,6 +162,7 @@
     </ProjectReference>
   </ItemGroup>
   <ItemGroup>
+    <ClCompile Include="Lower.cpp" />
     <ClCompile Include="Replace_Char.cpp" />
     <ClCompile Include="Replace_String.cpp" />
   </ItemGroup>
diff --git a/StringTools/Test/Test.vcxproj.filters b/StringTools/Test/Test.vcxproj.filters
index e159865..c10488e 100644
--- a/StringTools/Test/Test.vcxproj.filters
+++ b/StringTools/Test/Test.vcxproj.filters
@@ -21,5 +21,8 @@
     <ClCompile Include="Replace_String.cpp">
       <Filter>Quelldateien</Filter>
     </ClCompile>
+    <ClCompile Include="Lower.cpp">
+      <Filter>Quelldateien</Filter>
+    </ClCompile>
   </ItemGroup>
 </Project>
\ No newline at end of file